Topic I've blogged about before
Not sure if you've followed the recent story about 18 yr old South African athlete Caster Semenya. To most people, she looks a little mannish for a girl.
This fact has led to gender-testing. The rumor is that the (as yet unreleased) test results show she has some form of intersexuality, and that Semanya is on suicide watch as a result.
I have no idea what the truth of Semenya's case is, I just wish her well. What I want to say is:
Our society is structured around the sexual binary. In virtually every life activity -- clothing, grooming, activities, sports, marriage (including gay marriage), employment, online communities, every form you fill out, which bathroom you use, on and on -- someone wants to know which side of the binary you fall on.
And it makes sense from a medical standpoint to have treatment methodologies based on typical human conditions. But intersexuality is much more common that one would think. And in most of the cases where we want to know whether you're M or F, it shouldn't matter.
And on a related/overlapping note, there are transgender people. In case you live in a cave, transgender is the state of one's "gender identity" (self-identification as woman, man, or neither) not matching one's "assigned sex" (identification by others as male or female based on physical/genetic sex).
I'm tired of people whose lives are convenient (because *their* physical and emotional/psychological genders happen to align) being stupid about transgender people. I know some transgender folks, and I am in awe of their resilience and courage in the face of ignorance and intolerance from idiots.
I suppose it comes out of discomfort on the part of the typically-gendered person, but that's no excuse. If that's you, read up on this stuff here, or here, or here, or here, or here, or on your own. Learn something. Then get over it, and have some manners. If you're already a nice person, feel free to ignore the above diatribe.