Quite the opposite. Biology is very much real, and as a Biologist, I should hope so. It is those who assert biology ends at the genitals who are doing a disservice to Biology and that is what I was calling out.

And I find your statement about assessing sex interesting. If genitals at birth are the convenient way to determine sex, why don't you use this information when making these assessments? And if you are making assessments about sex in the absence of this information, is it truly sex that you are making an assessment about, or is it gender expression?

I'm using gender expression which is usually very much aligned with sex. Someone born a woman is most likely gonna have long hair or will be missing facial hair when they're older. They're going to have rounder hips and breasts too during/after puberty. Someone born a man is likely going to have broader shoulders and likely have facial hair too during/after puberty along with more muscle development.

Of course looks can be deceiving but the sex of strangers walking about in public is of little concern to me so I will assess sex superficially and not really care if I'm right or wrong.

I would say the suggestion that transgender peers are going to make other kids transgender, based on incredibly specious evidence, is problematic.  Rowling even recognizes just how problematic it is since she goes out of her way to clarify that being gay is an innate trait, although I'm fairly certain we could find the same kind of "evidence" to support the idea that peer groups can transmit the gay (I would imagine gay people are more likely to befriend other gay people, are more likely to come out if their friends do, and that we can find parents who blame their child coming out on gay peers). 

Whether it's hateful or not, I don't know. I don't like to ascribe intentions to people, although Rowling's post definitely indicates she was researching with an eye towards her conclusion.  Regardless of any intention though, spreading misinformation is harmful and should be called out, especially when it comes from a prominent source who (although she shouldn't) will be taken seriously by a lot of people. 

Since we're hearing these criticisms of gender critical feminists, I thought it might be useful to also include a short speech by a noted gender critical feminist (a more principled and weathered one than J.K. Rowling I mean) as well so that we might actually get a perspective from a veteran of this movement on their own terms. To that end, below you will find a speech by Meghan Murphy, who owns the Feminist Current web site you may have noticed I link to sometimes. It was given at the Toronto Public Library late last year amidst large demonstrations outside, mostly by trans activists disingenuously associating her with, of all things, the Trump border wall and "fascism" and "genocide" and other assorted hysterical claims. The trans activists had called upon the library to cancel the event because of who the speaker was. (It's a movement that I think you'll find struggles to tolerate concepts like free speech, dissenting views, and dialogue.) Every ticket sold. The video includes only the speech itself (not the Q&A that followed and such), which keeps it just under half an hour. I picked this one because I've found it to be Murphy's best and most succinct talk on the subject of gender identity. Without further adieu:

Hey not talking about open ended things. I`m more talking about the story is truly finished but the author keeps talking about how he interpret things in the work he wrote instead of putting that into the story itself.

"According to the trans movement, we are not women, we are cis-women, which apparently means we identify as the gender assigned to us at birth. This is insulting. I am not a 'woman' because I identity with femininity." *hold for applause*

This seems to be a pretty core part of the thesis of "gender critical" feminism, and it feels to me like a huge misunderstanding of what that statement actually means. I understand the perspective of this from an "abolish gender" perspective, however, I think we come to an issue when we talk about identifying and what that means. To "identify" as a woman, is not to embrace femininity but simply to speak about how you think about and name yourself. If you see yourself as a male and you prefer male pronouns, that generally means you identify as male. It does not say anything about your relationship with masculinity.

That is because gender identity and gender expression are not interlocked. We can identify as a female while expressing as masculine, and that is entirely valid.

It seems like the "gender critical" philosophy completely misses this point and fails to see how this philosophy largely aligns with the feminist critiques of the concept of "gender". It is allowing a full, independent range of expression, no matter how you identify. It is a means of stating that your identity as a "woman" does not define who you can be.

Saying "I am not cis" because you don't align with all of the stereotypes of femininity is an embrace of this ignorance, and it seems to play into those same masculine/feminine stereotypes that you are criticizing, but this time attaching them to trans individuals. A masculine trans woman is just as valid as a feminine trans woman. It isn't how you express your gender that defines your identity. This shouldn't be a difficult concept for those familiar with feminist theory, so I don't understand the roadblocks. A lot of trans individuals express as agender.

So much of "gender critical" theory is based on not understanding trans theory and trans individuals and this video made that abundantly clear.

And so much of her video isn't devoted to "gender critical" ideas, but instead to complaining about mistreatment. Those complaints may very well be valid. I'm sure that she was treated poorly by some people and that is obviously abhorrent, but it does not speak to the strength of your philosophy to point that out. Others being rude to you and mistreating you, doesn't make you more right.

EDIT: By the way, there's more that I want to say about the feeling of safety, but I'm not sure when I am going to get around to it.

(I left it at that because I think your core case was made here and this is what I aim to reply to tonight.)

That, to my mind, only shows gender identity to be even more arbitrary and disingenuous concept than I'd previously believed. If a guy can just claim for all legal and social purposes that he's a woman without even being expected to change anything about himself to indicate as much -- if he can just continue comporting himself in a socially masculine way and everything -- and I'm seriously expected to just buy that he, with his full Taliban beard and all, is really a woman on nothing more than his personal say so, then that only shows how capricious and intellectually dishonest this whole phenom is.

The essence of what gender critical feminists believe about womanhood is that it's something that exists objectively, materially, and has real-world consequence. Womanhood is not just a feeling that anyone can claim. You cannot just identify your way out of patriarchal repression. Phenom like the polls showing the vast majority of people prefer male babies and societies where fetuses are commonly aborted if it's discovered that they're female go to show that social misogyny begins to affect one before they're even born, let alone able to conceive of a gender identity for themselves. Patriarchal oppression doesn't care about your gender identity, it cares about your physical chemistry and defines your worth accordingly. That, in fact, is why trans-men face discrimination and under-representation even within the transgender movement: because they are biologically female! It's no coincidence that they have the higher rates of depression and anxiety are more likely to try taking their lives.

Sexism is called that for a reason: because it based on your sex! To the extent that that simple fact is ignored, it becomes impossible to recognize sexism when one sees it, and thus to resist and defeat it.

Its tough for me to reconcile this idea that trans women must be feminine to be valid, with femininist critiques of gender. As the woman stated in the video, no one should be defined by stereotypes and nobody conforms perfectly to society's ideas about femininity and masculinity. The "gender critical" perspective seems to throw that away in its criticism of masculinity from trans women, while simultaneously criticizing feminine trans women as wearing a costume and being stereotypes.

When I hear these two pointed criticisms, it largely sounds to me like an insistence that trans identity is never valid. This is the core transphobia that "gender critical" is based on. No matter how rosy your prose or how righteous your indignation, at the end of the day, if you look at what is being said, it is hard to ignore that. You seem to not even attempt to disguise these beliefs in this post.

As for your statements about womanhood, I feel that is an extremely limited way of looking at things. While a trans woman may not have had the experiences of girlhood, she also often didn't have the experiences of typical boyhood, and she often does experience many of the same patriarchal systems when living as a trans woman, often amplified by the fact of her trans identity. This assertion that every woman must have x, y and z experience in order to be a real woman seems to blatantly ignore the variation in lived experiences of women, in addition to ignoring the experiences of womanhood from trans women. There is no reason why we cannot reconcile both of these experiences in a fight against patriarchal and misogynistic norms. Similarly, the validity of trans identity doesn't erase the concept of sexism. If anything, it provides an important case study on it. Similar to twin studies, we are able to examine the perspectives of individuals and how their lived experience differ when living as a man vs a woman. If anything, this amplifies the validity of criticisms of sexism. In no way does it lessen it.

And since I'm already typing, I will speak briefly about the feeling of safety that the woman spoke about in the video you posted. She mentioned a scenario in which a woman at a woman's shelter felt unsafe by the presence of a masculine trans woman. First of all, I do believe that this feeling is valid. I believe that a shelter designed around providing people safety should be willing to take reasonable steps to ensure that feeling of safety. This applies for situations regarding both cis and trans individuals.

Second, I believe this to be a fear of masculinity, not whatever biological state that individual existed in. Were it a masculine trans man, I don't believe anything would have been different. Do you think she would have been comforted by the knowledge that this person once had a vagina? Do you think she even asked whether the individual was a masculine woman, a masculine trans man or a masculine trans woman? What means did she have of assessing the sex of this individual?

Even so, it shouldn't be hard to imagine a situation in which a woman feels unsafe by the presence of a trans man. What then? If we are to codify sex based rights in law, a masculine trans man would be granted access to sexed spaces, no matter how uncomfortable that makes both parties feel. So what is the solution to this conundrum? How do we reconcile this issue in a way which upholds the feminist perspectives on gender?

My belief is allowing people to make that decision for themselves is generally the best for everyone. There will be times when issues come up and as a society, we need to come up with a means to address this, but holding on to sex does nothing to actually address these issues in many cases, while directly putting trans people in danger, and harming their emotional well being.

As I wrote in the OP, it is hard for me to have a clear position in these questions, which doesn't mean they aren't important. But one thing that seems clear to me is the following: it should be possible to accept that biological sex exists and is a defining feature for the majority of people (and actually most animals) there are two defined sexes. Only a minority actually are intersex people (less than 1%). But the sexual dimorphism (meaning specifically male and female attributes) is more fluid, and there are men with female features and vice versa, which doesn't change their biological sex. Aside from that there is a gender identity, that is way more fluid. This gender identity may or may not conform with the biological sex and it may fall outside of the categories of only the two biological sexes.

So in conclusion I think, it is possible to accept biological sexual identity and trans identity at the same time. And that shouldn't be a problem at all.

Naturally a problem arises in the establishment and perpetuation of safe spaces and rights, that are specific for some identities. And I think (correct me if I am wrong), that is what the discussion at the core really is about. Feminists fear that their hard won safe spaces and rights might be threatened, while trans activist want (rightfully so) claim also rights and safe spaces for themselfes. I personally think all the claims that accepting the identity of one group denies the other group their identity is actually not helpful, but instead the real problem of how the rights of each group conflict (or seemingly conflict) is something that should be solved instead.

Maybe I fail to see some part of the problem and maybe I am to naive.

A transgender's perspective on Rowling's tweets, a well-thought out video in which Blair happens to make fantastic point later in the video by saying:

"Right now, I feel the world isn't divided into left or right, conservative or liberal.... what I see these days is that the world is divided into people who can have a meaningful nuanced sensitive issues and people who can't". 

And I totally agree with her.