Gonna pick on Fistful here for a sec. Not trying to be mean, but he has the best "example attitude" for this, as NOTHING will convince him that allowing this in any way, shape, or form is acceptable*
So there's those on the Right covered.
The Left would fight against this plan, probably saying something along the lines of "but it isn't the same!"... never mind that, in legal fact, it IS. But then the Left wouldn't have such a great wedge issue to use, keeping gays voting as a block for the Democratic Party
*Not trying to argue whether or not your views are right, moral, just, or anything else. Just using them as an example, no judgement implied