Ann Althouse (one of the better commentators on the law today) surmises that "rational basis scrutiny is the appropriate level of review" for this issue.
My problem with this approach is that "rational" has ceased to mean "using reason" and has devolved into Rationalism in its more refined form of using human thought apart from revelation at all to derive truth.
My comment: It depends really on what you believe the basis for rationality itself is. It is not enough just to declare that arguing against order presupposes it (it does).
The problem with many good and insightful thinkers is that they are standing with both feet planted firmly in the air. That is, you presuppose an ordered, moral universe and ignore the metaethical questions that such a worldview demands. In doing so, you slip in a utilitarian assumption with the deftness worthy of a card sharp (I don't think you see it yourselves, frankly).
Rationality itself demands presuppositions which land you in "Moralsville," where you MUST let those damned fundamentalists have a place a the table. Of course, that changes the whole nature of the debate.