Were there no threat of a federal court, and ultimately the Sup Court, imposing gay marriage/civil unions then I'd probablly agree with you. As it is, many in Congress from both parties claimed to oppose gay marriage, yet also oppose the Amendment on the grounds you speak of; i.e. that its a matter for the states to decide. I wonder how many of these politicians parroting this line are serious, and how many are simply lying. Will Senators McCain and Conrad, for example, vote for an Amendment IF there is a Sup Court imposition of gay marriage/civil unions? (and the 'civil unions' part is key, because while I will admit they enjoy significant support from the public, the imposition of them from the courts is no less radical than full-on gay marriage -- the only proper course for the courts is to stay out of it).
Part of me wishes that Frist would instead try to call these Senators on their stated beliefs, and instead offer up an alternative Amendment, like the one Orrin Hatch has supported. I can't remember the exact wording, but it either explicitly empowered the states to handle it, or explicity removed the matter from consideration from federal courts. Since such language would let states set any policy they want, I can't imagine how a McCain would justify a vote against it.
Very well analyzed. I would be interested in one that permitted states to do as they wish, but the DOMA does that now. I'm not sure how the USSC would rule against DOMA, given that it complies completely with Article IV, which gives Congress the authority to make rules pertaining to the Full Faith and Credit Clause. If so, it would have to be a convoluted reading of the 14th Amendment, and if so, even a constitutional amendment would have to be constructed so as not to conflict with the 14th. So yes, I'd like to see that.