Spanking: art, or pornography, or both?

Patty had the opportunity to check out a cool retrospective on artist Norman Rockwell this past week. She could not help but notice after all the recent hullabaloo about Bobby and his pervy wife that Rockwell has several paintings depicting children being spanked or with their pants down:

So, this is not pornography because of the intent of the artist? Surely there are those out there who get their rocks off on innocent stuff like this. But we accept this as art nonetheless.  Interesting, no?