1. The scientific data do not support the claim that sexual orientation is a "genetic condition". I've mentioned the monozygotic twin research before: the concordance rate for homosexuality in MZ twins is about 50%. Thus I can have the same genotype as my brother or sister even though one of us is gay and the other straight. As with most psychological characteristics, sexual identity is the product of a complex interaction of genetic and environmental factors.
2. Political activism and support for political causes are not predicated on biological research. Did we need scientific research in the 1950s demonstrating that people are "born black" to garner support for the civil rights movement? Blacks don't deserve equal rights because of their genetic characteristics; they deserve equal rights because they're people. --And just so for gays and lesbians. What's next--the right of political expression is only available to those who can document that they were "born" with a certain political orientation?
3. The notion that race is biological is itself drawn into question by population geneticists and anthropologists. There is more genetic variation within the group we socially identify as "African" than there is between "Africans" and "whites". Moreover, there are dramatic cultural differences in the social definition of race (in one society, people with somewhat different skin tones will be considered the same race, and in other societies they will be considered different races). There is nothing natural and necessary about the specific racial categories our society (or any society!) uses. Given that race is a social construct rather than a biological one, it turns out that the analogy between sexual identity and racial identity is apt.
Miles