William Saletan draws a distinction between gay marriage and polygamy that beats everything I've said. The key he, says, is to remember that marriage isn't based on how many people you'd like to sleep with:
The average guy would love to bang his neighbor's wife. He just doesn't want his wife banging his neighbor. Fidelity isn't natural, but jealousy is. Hence the one-spouse rule. One isn't the number of people you want to sleep with. It's the number of people you want your spouse to sleep with.Makes sense, right? Saletan goes on to confront Charles Krauthammer's column conflating the two issues:
Krauthammer finds the gay/poly divergence perplexing. "Polygamy was sanctioned, indeed common" for ages, he observes. "What is historically odd is that as gay marriage is gaining acceptance, the resistance to polygamy is much more powerful." But when you factor in jealousy, the oddity disappears. Women shared husbands because they had to. The alternative was poverty. As women gained power, they began to choose what they really wanted. And what they really wanted was the same fidelity that men expected from them.
Gays who seek to marry want the same thing. They're not looking for the right to sleep around. They already have that. It's called dating. A friend once explained to me why gay men have sex on the first date: Nobody says no. Your partner, being of the same sex, is as eager as you are to get it on. But he's also as eager as you are to get it on with somebody else. And if you really like him, you don't want that. You want him all to yourself. That's why marriage, not polygamy, is in your nature, and in our future.
And just like that, this makes sense. Too bad more people don't read Slate.