Banning things you don't like is wrong. The Brady campain makes the SAME argument when it wants to repeal the 2nd amendment and ban guns. It's just as wrong as anyone's arguments to repeal the first amendment "for our own good"
On that note, I'd like to point out the disaster that was the last time we passed a constitutional ammendment banning something...
On the same note, in a society with a ~40% divorce rate, how does gay marriage or civil unions harm the institution?
On adoption, child rearing and such, I'd rather a child be raised by a dedicated couple, whether that be a man and a woman or otherwise, than a single parent - even if that parent is straight. Definitely better than a fighting or abusive set of parents. Meth, dope, alcohol addicts. The list goes on.
I'd hope, at least, that the adoptive parents would be as understanding of their child(adopted or otherwise)'s orientation as they'd hope their families were of theirs.
I say let them do what they want, as long as they're consenting adults. Even adopt children, provided they can meet othe rest of the requirements of not having a screwed up home.
Honestly enough, the percentage of gays is low enough for it to be, ultimately a null issue. I'd rather concentrate on balancing the budget, reducing waste, etc...