Is being gay a choice or is it genetic? I believe that it is a choice because of a lack of scientific evidence of the "I was born that way" theory. Other groups would have you believe that you are born gay. Which is fine, but it makes for interesting situations where you can legally discriminate....errr...use information in interesting ways because the person was born gay.
For example (and I think I probably have picked the worst example I could possible think of), sickle cell anemia mostly affects dark skinned people. It is a fact that cannot be hid from. So if you were going to do a mail out asking for volunteers to help with a study, I probably would be most effective to send out the mail to the nearest inner city or just registered democrats.
This article points out a situation that I had never thought of before.
Source:"To the dismay of gay-rights activists, the Food and Drug Administration is about to implement new rules recommending that any man who has engaged in homosexual sex in the previous five years be barred from serving as an anonymous sperm donor."
The FDA says it is because homosexuals get aids and they should not be allowed to donate sperm. That sounds nice on the surface, but upon closer inspection that does not make sense. In reality, anyone can get aids, so you should test everyone. Anyone can lie easily the forms which ask you to disclose this personal information. You can also lie about being gay. Which since there is not a gay test there is no way of catching this person.
I personally do not see any reasons why a gay man cannot donate sperm, as long as his sperm is clean of disease and his sperm is packaged in bright rainbow colors so that the woman who get is knows that her child might turn out gay, though there is not scientific evidence of that.
update: Upon reading the title of this post, I thought it might be a good idea to clarify. I AM not gay, though I might have been born that way (I have seen on scientific evidence to the contrary)