There is usually reason to tradition though the reason not be superficially discernible. Hey, I think I wrote something Burkean. ;-)
Religion, in addition to the worship of God, was really the only "history" and "rule of law" we had for millenia.
Here there's a problem. Today we have, for better and worse, secular (government) law. Why, I don't know, but we've given to government the power to 'sanctify' marriage. Gay marriage? Stripped of all emotion, this is a legalistic thing for the fact of government having superseded religious institutions as the agent of legitimacy. Marriage? Term heterosexual marriage as matrimony (or some such) to maintain distinctions.
Those are just some thoughts. I'm not going to get in to a dog fight over the thing.
You'll get no fight from me. I hate that kind of thing :0)
I definitely believe in a distinction between a union based on procreation and one simply based on love. I would call one "marriage" and the other "civil union" but I'd be open to Marriage vs. Matrimony or whatever.
At the risk of flame wars (in which I will not participate) I can see nothing in the Constitution that should bar gays from Constitutional rights. But that would be called a "civil union."
"Marriage" is a religious sacrament. If gays can find a church to sanction their marriage, fine. But the government has no right whatsoever to redefine the ages old definition of "marriage." None whatsoever.