Nothing to be added about the marriage, as of yet. We'll wait for the fundies.
As for adoption, I, too, see how it's more complicated, but still the overall "score" remains positive.
Even if a gay couple's adopted child gets bullied, it's still a huge improvement from living in a children's home. And as you know, children get bullied anyways, I, for example, got bullied for being fat and not considering school the worst thing that ever happened to me. Curiously enough, they made school the worst thing in my life for the time I was on the same class, but I'm digressing.
True, there's more than bullying to it. Like explaining the kid why he has two fathers/mothers instead of one of both. But the problem here is less about telling them their parents are gay and more about explaining them what's the damn difference. Sex, after all, is a big taboo, and you can't tell a <10-year-old about that shit.