Yeah, he really clobbered me with that argument.
I'm more interested in your response to the Constitutional questions. Do you propose to ban pornography in a manner consistent with the original intent of the Commerce Clause? If Madison's account of the nature of the power given Congress to regulate commerce is correct (I think that's a pretty safe bet - he wrote it), then what you are proposing is not a valid exercise in regulating commerce (among the several states, or otherwise). If it is indeed a "moral imperative", you should be prepared to demand an amendment to the Constitution, or to take up arms against the government if they do not.