I disagree that Gay is a birth defect. We can reproduce, as long as we aren't sterile, regardless of who you enjoy having sex with. I'd much rather see two guys find a serogate or two lesbians get a turkey baster, then see one more hillbilly, backwoods, uneducated couple of SOB's pop out another dumb kid.
Not to mention, it's been suggeusted that Gayness has had a long time role is societies; gays & lesbians have long been considered shamans in different cultures, perhaps because they straddle the masculine & feminine, and were sought out for council. In the ancient world, they believed that soldiers that loved other men/soldiers were more ferocious in battle, Hell, look at Achilles and then Alexander The Great. Etc.
Personally, I think stupidity is a birth defect, geez, look at our culture.