One does not choose to desire anything; thinking otherwise is what Ryle called a category mistake. I do not choose to desire a glass of water; I just desire one. The same goes for belief. I can no more choose to believe in God than I can choose to believe that there is a computer screen in front of me. That being the case, it matters not a lick whether one’s sexuality is biologically based or otherwise.
What really seems to be at the heart of dispute is whether one’s sexual orientation can change. Available evidence, especially with regard to males, is it can not be changed. Orientation seems to be far less varied than behavior. (Women who identify as bisexual respond to erotica of all sorts; their bisexual male counterparts on the other hand only respond to one or the other.) This has led those opposed to fundamentalists to claim victory. Both sides are guilty of confused thinking though. Just because sexual orientation can not be changed does not mean that this settles the issue. Pedophilia also seems to be immutable, but that does not make diddling kids morally permissible. Homosexual behavior is morally permissible because there is no harm in two consenting adults of the same sex engaging in sexual behavior and with regard to morality no harm no foul.