What if, some years from now, a latter-day Andres Serrano turns up at the Drawing Center's new home at Ground Zero, with an American flag submerged in a tub of urine — calling it, say, "Piss Flag"? Or with an image of the Twin Towers covered in cow manure? Could such outrageous "art" be banned from the site? If that sounds ridiculous, just think back a few years — to Serrano's "Piss Christ." Or to the Brooklyn Museum's 1999 exhibit, "Sensation" — featuring the Virgin Mary covered in elephant dung. Gov. Pataki — despite his assurances to the contrary Friday,...