Stuart Buck has a great post on Laurence Tribe and his momentary disdain a few years back for a "laid-back jurisprudence of a morphing Constitution." On the broader point raised on the Volokh site, about people's constitutional theories hewing to their policy preferences, I think that's true up to a point, and it's most true where the constitution is most ambiguous. But there are neutral principles, there is a historical record; the document is not just an ink blot.