Should sex defining traits be treated? Depends, isn't Down Syndrome having a 3rd Chromosome? That should be treated always. I dunno what YY give you, an infertile female? If so, yes that should be treated. As for other traits, I'm not aware of any positive mutations in this aspect, so IMO yes they should be treated.
As for the surgery itself, I think it's gross. I'd be more into converting people genders if they actually could to it accuratly. It doesn't matter if she is lacking ovaries, but the idea that some girls out there have inverted penis's for vagina's....that's not a substitution, and while that individual might be a happier person, what about the people she sleeps with? Do they not have a right to know if they are having sex with a Vagina or an Inverted Penis?
Should people who have participated in sex change opperations, at the level of quality they have now, be treated in the same way people with HIV are treated? Legally (In Canada) HIV carriers have to inform their sexual partners about their condition before they can have sex. Thus if someone contracts HIV and wasn't aware of you carrying, you can be in serious trouble. Sex Change doesn't have any contractable desease, but IMO it's equally as unwelcoming. Should we force these people to tell their partners about their conditions?
Can you cure acceptance to homosexuality? If not, is it wrong to offer homosexuals who wish to be heterosexuals under pressure a way out?
What about homosexuals with or without family pressures, who just want to be heterosexual? What about a Mama's Boy who just wants to make mom proud and give her grandchildren, and have a family?
A "cure" may be administered incorrectly, in some cases, but is it worth not having at all?
What about a cure which turns homosexuals into bisexuals, favoring the opposite gender. What's your thoughts on that? This way a homo gets everything, does he not (Family, maybe children, but still stays gay).
I'd say altering chromosomes would be near impossible, merely because of the fact that it's the base building blocks. Turning an X into a Y would introduce more defects than it would fix, provided the patient lived that long...But for the sake of the theory, if you COULD, I'd say that changing a defective gene in order to allow people to reproduce might be a bad idea, since said bad gene could most likely remain in the offspring.
I don't know? Are men entitled to know before sex if a women's breasts are fake? Are women entitled to know if a man isn't adequately equipped before sex? HIV is one thing, because it can have life-altering consequences, whereas those who cannot tell a constructed vagina from a real one would never know any better. It would be a case of ignorance is bliss.
I think you have as much chance of developing a drug to administer to people to accept homosexuality as you do with the bisexual drug that you mentioned. I'll explain why when I get to it at the end.
A homosexual who wants to do stuff to make their mother proud would be classed as working from outside influence. I once heard a story about someone who wanted to be closer to her mother (they were rather apart) and started considering smoking just to share something in common. Altering your life for the will and happiness of someone else is a bad idea, no matter how you look at it. It would have to be a decision that they'd have to make for themselves.
Given the amount of "what ifs" here, like the one mentioned above, I'm starting to think that maybe the world isn't ready for such a "cure", based on intentions of others, directly or indirectly. A gay couple who wants a child would generally want it with the one that they love, and I'm pretty sure that they've gone a long way with turning one reproductive necessity (an ovum) into the opposite gendered equivalent (a sperm), in order for homosexual couples to have children, much more progress to it's goal than a homosexuality "cure".
For the bisexual drug thing, I'll explain a theory I have on the matter. In a way, everyone is bisexual. It's not black and white, merely tones of grey. What sets bisexuality apart from the others is the "thresholds" that differ between people. The threshold is like a balance, a tipping point for how much one enjoys, for instance, heterosexuality over homosexuality, or vice versa, that one is distinctly better than the other in noticable magnitudes, thus the fields of homosexuality and heterosexuality. Bisexuals tend to have a much wider threshold than the other two, since they encompass a lot more shades into their mindset of attractiveness. A lot of bisexuals still have a preference to one side or the other; that's just different shades of grey in the scale between full hetero and full homo.
Now, for a bisexual drug to happen, it could realign your "bisexuality meter", but the tolerances would still remain. This would hardly work at all. The only way I'd see it is to increase the threshold by some kind of "acceptance drug" (as explained above), which would keep their orientation as strong hetero/homo, but still have a developed tolerance for the opposite side of the spectrum. Is this feasible? Absolutely! Will it ever be a reality? Nope. The reason is politics. Anti-gay advocates would herald this as a first step to eliminating homosexuality......until they find that it would have the reverse effect on full hetero people (making them open to homosexual encounters), to which they'd burn the research centre to the ground.