Well, lets say that homosexuality is a "condition" and somewhere down the line there is a therapy developed with which to prevent it. I would imagine it would run along the same lines as any other genetic manipulation. In essence breeding out perceived flaws in the human race. This can go beyond homosexuality to embrace females, short people, dark skinned people, hell, everything that Hitler despised to be honest.
Sure we could do that, and lets face it, many people would be on board for that. I bet even in this small internet community people would be willing to subject their potentially conceived embryos to "treatment" in order to prevent "defects". The question is, what is a defect?
I mean really, David, your "gay" threads are interesting and thought provoking but I can't help to always pick up a note of self loathing in them. So, let me ask YOU... if there was a "treatment" for homosexuality available when you were inutero... do you wish your parents would have administered it to you?