The children need to be supported. The homosexual couples don't.
Gays raising kids is bogus, and agencies that let gays adopt are letting their wards down. Individual gays may be capable of raising a kid properly, but will they want to? Can you tell me in good faith that liberal, out, committed gays will pass on to kids any but their own gay paradigm as a worldview? They couldn't, without being total hypocrites, and I doubt that any of them would bother to try. So how do gay parents raise straight kids to be straight? Or do the straight kids raised by gays wind up having a much, much higher rate of homosexual accommodation and bisexuality than straight kids raised straight in straight families that impart traditional mores?
I think you know the answers to those questions. Gay parents can't, they wouldn't, and they won't raise kids to be traditional straights, but gay-friendly "reconcilers" instead, imparting the countercultural gay Weltanschauung to kids who would otherwise have a straight one.
Result: queer kids who merely "prefer" the opposite sex.