Spence, maybe you'll tell us that the World Health Organization doesn't know as much about this stuff as some gay rights group, but here's some pudding that's just chock full of truth. You will find it to be inconvenient truthm, and thus not to be accepted, but try telling a scientist that it's not chromosomes that determine your sex...
"Humans are born with 46 chromosomes in 23 pairs. The X and Y chromosomes determine a person’s sex"
http://www.who.int/genomics/gender/en/index1.html
Also..."Gender, typically described in terms of masculinity and femininity, is a social construction that varies across different cultures and over time"
Gender is what you are referring to, which I guess can be said to be interchangeable. Not biological sex. And when one goes into a public restroom, it's (hopefully) not to engage in a social experiment, but rather to take care of a biological function. That used to be a simple, non-controversial topic. Not anymore. Unbelievable.
Enjoy that pudding.