We should not allow a "biology v. choice" framing of the rights debate to continue. If we do, we will likely find ourselves backed into a very unpleasant corner. We will be forced to argue that we are helpless over our sexuality, and then will be faced with the very frightening prospect of arguing in favor of a medical definition of sexual orientation -- which can then be used against us when people decide to start looking for "cures." For make no mistake about it: if they think they can "cure" us by counseling us into making different choices, they will be no less likely to try to "cure" us of a sexual orientation that they can frame as a disease. If there is a "gay gene" we should be very wary of what happens if it's found. It will then be possible for genetic testing to "discover" the sexual orientation of a child and gene therapy may be used to "fix" that child. We've been there before in less technologically sophisticated ways.
I sort of feel this way about various kinds of gender essentialisms. Even if it were the case that 'most women are like x' and 'most men are like z', I always want to ask: What about those that don't fall within those norms? Shouldn't they be able to freely be themselves, anyway?