Where lies the ignorance?

At the following link, a columnist attempts to ridicule a political actor for her not knowing where in the Constitution one can find "the separation of church and state."  I, for one, don't know where to find such a principle in our Constitution, though I do understand why we *should* interpret the Constitution in a way that respects both the independence and *possible* interaction of these two "sovereign" spheres.  Whatever the referenced politician's shortcomings (they are considerable, in my view) or merits, she surely makes, even if unwittingly, a good point about our Constitution:  That document simply does not make the separationist point, even if the interpretations of the Constitution that march in the separation direction, or at least some of them, can be defended on honorable grounds. I fear that the columnist's attempt at ridicule backfires.