First of all it's disgusting. But as a man I have a serious problem with women (pre-op) using the mens bathrooms - there have been numerous studies showing that females use the restrooms more frequently and longer than men on average. You can see this in action at any opera or other public gatherings with equal gender representation. So it is frankly sexist, against males,to allow females to use male (or unisex) restrooms, because it leaves us (males) with longer lines and longer waits. This should be based on atomy, and yes if you are post op I'm fine with you using your post-op restroo of choice, so long as it matches your genitals, but that's all it should extend to.
Any non trans person that supports unisex or trans friendly bathrooms are traitors and throwing the rest f us under the bus to placate an outside group you dont even belong to. Being a traitor to your kind is the most disgusting thing a person can do.