Since I missed this way back, I just wanted to make a comment:
While it may not be "innate" (i.e. environmental effects may influence it, not purely biology), I have an exceptionally hard time believing that someone "chooses" to be a member of a marginalized group in society, and all the negative stigma associated with it. If it was merely a choice, wouldn't people choose to become heterosexual rather than killing themselves because of being ostracized for being a homosexual?