I'd say it's very much an individual issue, and not a lump-sum issue at all, and THAT is where people are making a mistake with this whole "sanctity of marriage" thing. You don't automatically get to have a good marriage just because you are straight or bi or gay. Just like you don't automatically get to be a good mother just because you are a woman of child-bearing age. It's individual: some people are cut out to be parents, others are not. Some people are cut out to be married, others are not. It's not a right (and by this I mean a biological right, not a legal right), it's a privilege.

I know plenty of stable het marriages. I know plenty of unstable ones. I know plenty of stable gay marriages. I know plenty of unstable ones. The line shouldn't be drawn through sexuality, but rather through individual ability and effort.