Well, if it's purely genetic, please explain how it hasn't been selected out? ;0)
Seriously, I don't care. I can't imagine why anyone would. My personal feeling (again, based on my own limited exposure and friendships) is that most of the gay people I know have some other mental problem - bipolar, depression, whatever. My gut is that homosexuality is associated with another disease state in the brain. If it is a mental disorder, that would explain why it hasn't been selected out.
YMMV.