Over at Volokh
Maggie Gallagher fights the good fight about same-sex "marriage". Of course she's already in trouble because she has already started talking about procreation. The problem is "procreation" has an embedded premise that, once accepted, leaves you in an increasingly untenable logical position.
Now, readers of this blog know my opinion on this. Like abortion, there's a right answer and a wrong answer. It's left as an exercise to each individual to figure out the reasons why the right answer is correct, and why the wrong answer is incorrect. There are both right and wrong reasons for the right answers. And in both cases, the solution is fairly obvious.
The problem with same-sex "marriage," is that there's no such thing. Because same-sex sex isn't sex. It's sex play, but it's not sexual intercourse. We wouldn't consider a couple married if they only engaged in oral sex, or sodomy, or masturbation, or frotteurism, or rubbed up against the furniture until they orgasmed, would we?
No, marriage involves sexual intercourse, and that requires no fewer than one woman and at least one man. End of debate. Therefore any social definition of marriage means we must have at least one woman and one man. For social reasons, we've determined polygamy isn't a good idea, so we limit marriage to one of each. Now really end of debate.