I don't think that you're missing anything. If civil unions become the functional equivalent of marriage, then they will differ in name only.
But, politically, that difference can make all the difference in the world!
It sounds like you're suggesting the conclusion that I had rejected out-of-hand.
Are you saying that the American public (remember, the Dims are only following the polls) are intentionally deluding themselves in the hopes the problem will go away?
It makes more sense to me for them (the public) to say "big deal, let the fags marry."
Shalom.