I was considering that myself. I mean, one aspect of censorship is "is the picture depicting a crime?" Take the following:
Case A:
A photograph of a man having sex with a naked 11 year old girl.
That's clearly a crime in progress. It's generally accepted that it should not exist because the act itself is illegal.
Case B:
A picture of a naked 11 year old girl with a man photoshopped in to be having sex with her.
The picture itself is depicting a criminal act, but no criminal act ever took place. The man is not having sex with the girl and last time I checked being a naked 11 year girl was not criminal. Under common decency, though, it is accepted as child pornography because even though the nothing illegal happened in reality, the photo, I guess, creates its own reality where it did happen and because of:
Case C:
A picture of a naked 11 year old girl.
Which is where we are here. Again, there is no crime here being committed in reality, but the idea behind censorship here is the intent of the viewer. You cannot guarantee that the viewer simply sees an 11 year old girl who happens to be naked. The viewer could commit a crime in thought, in the reality of his own mind, where he is having sex with her. Is this the level of censorship we're comfortable with? Thought crimes?
Furthermore, why is sexulaity and nudity so heavily censored in the first place? You can create an equal scenario for each case related to violence and, in fact, at most Case A (picture of reality) will be censored, if that.