I'm against gay marriage for all of the (non-bigoted) reasons that you've heard cited by other conservative commentators. Civil unions I can live with.

Initially I was somewhat inclined to accept the proposition that some states would sanction gay marriage, as long as other states weren't forced to recognize it.

Well, after reading these questions from NRO's David Frum, I realize that such a halfway measure won't work.

Allowing just one state to make legal gay marriage creates the same sorts of problems that the Dred Scott decision spawned shortly before the civil war. If gay marriage is the law anywhere it makes gay marriage the law everywhere.