Wow...so....much....
Here's my take on all this...
Gender is a physiological condition (as stated previously). There are more than 2 configurations, but it's still a biology trait and not a psychological trait.
A male has a penis and does not produce milk. A woman has a vagina and can produce milk for her offspring. (These are "normal" genders..and there's only 2)
That having been said, there are irregularities that occur that can mix any of the traits I just mentioned. If your biological body doesn't fit the 2 normal genders, meaning you physically have traits that are a mix of the two, then you are entitled to have a different gender (such as hermaphrodite, which is someone who exhibits traits of both genders)
Now, the problem with there being "more than 2 genders" is that it looks like the Unown alphabet and it's absolutely absurd. Unless you fall into one of the MAYBE six biological configurations, then you're NOT an amorphous toaster unicorn, you're someone with a PSYCHOLOGICAL disposition, which is NOT related to gender.
It IS possible for a man to have elevated estrogen and think and feel more like a woman than a man, but if he's got the hardware of a male, he's a male...doesn't matter how his brain works. By that logic, we need separate accommodations for not just all of the genders, but each of the abnormalities within each gender. For instance, lets say that the man I mentioned above who thinks he is a woman...is into women. Since he identified as a woman, that would make him a lesbian. So which bathroom should he use? Which locker room should he use? (and here's where my point really comes in...the locker room)
If there are 31 flavors of human and there are only 2 locker rooms to change in...where do you sort them into? Does the lesbian man go into the women's locker room or the men's locker room? Since he's into women, he would be a potential predator in the women's locker room even though he identifies as a woman and the women would be upset to have a man changing in there. You could change the variables in this scenario to pretty much anything you want. A gay man in a men's locker room or a lesbian woman in the women's locker room prevent their own issues, but when you start letting people decide their gender, it makes things even worse.
You can call yourself a sparkly segmented platypus who is maysexual, but only on Tuesdays...that's up to you.
But gender is NOT a state of mind...not even a state of the chemicals in your brain (as I believe sexual preferences and such are, mostly, a chemical difference in the brain and NOT a conscious choice).
If you are PHYSICALLY female, you're a female. If you are PHYSICALLY a male, you're a male. Anything else is a personality trait, not a gender.