In which P.Z. Myers explains why Newt Gingrich is moral, and he isn't.
The Republicans support a version of marriage that rests on tradition, authority, and masculine dominance, and everything they do props up one leg of the tripod or the other. Public piety reinforces religious tradition; the insistence that there is one true form of marriage, between a man and a woman, which represents a legal and social commitment is part of the authoritarian impulse; and of course, if a man steps out of the matrimonial bounds, it's an expression of machismo and patriotism and entitlement.
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Now look at those dirty rotten hippies, like me. We say the ties between a couple should be made with respect and affection, not the strictures of law and precedent; letting gays marry, for instance, strengthens the public approval of our kinds of bond, while weakening the authoritarian bonds. Our ideal is a community of equals, while theirs is a hierarchy of power, a relic of Old Testament values in which marrying a woman was like buying a camel, a certification of ownership, and nothing must compromise the Big Man's possession of properties.