"Is it genuine bigotry to believe that a child needs a father and a mother?"
Yes in short.. and when you use what amounts to mobs to try enforce this legally, Yes.
"Is it mean-spirited to believe that the legal institution of marriage is far more about children's and society's ultimate needs than it is about the emotions and desires of the wedded adults?"
No, that's just plain stupid. And to make it worse, you know it. The "one mother, one father" thing only makes sense if you subscribe to a host of other utterly nonsensical bullshit. Let me ask this in my own snarky bigoted way:
If having a mother and a father is the only way a child should be raised, why aren't we making an amendment to take children away from single parents, to make divorce illegal, and require a license to breed? Oh right, because no one would fucking put up with that bullshit. The argument is old already, but I will regurgitate it: If we put other civil rights up for votes, they would lose. And the big one: If we had a constitutional amendment vote on banning "protests at military funerals" it would probably pass. We live in a representative democracy to PROTECT the minority from the tyranny of the majority. The minority is never really a tyrant, it's just that the majority is a bunch of babies.
I get it: you don't like LGBT people. It's not really cool to say it anymore, but you can still try to at least keep them down. It's a good thing that people still die -- after a long life of course -- otherwise, ideas would never get a chance to progress.
Remember when you're out there screaming your hate for this ungodly thing, or that unchristian whatever:
We look about us, on the streets and in the subways, and discover that we are beautiful because we are mortal, priceless because we are so rare in the universe and so fleeting. Whatever we are, whatever we make of ourselves, is all we will ever have--and that, in its profound simplicity, is the meaning of life.-Phillip Appleman originally quoted here