I was reading a story a while ago (I don't recall enough about it to even search to provide a link) that talked to some pedophiles. Specifically, people who had the urge to interact sexually with young people. It talked about how some of them knew this was a bad urge and acted to counter it. One of the ways they did that was to get hold of fictional child pornography (stories, drawings, animations, etc). This allowed them to feed their urge without hurting anyone.

The idea behind the disucssion/story was that pedophilia (the desire) is a condition (like any other we treat; alcoholism, depression, etc). Treating it like that, looking for ways with the urge to avoid hurting people, was a reasonable approach. It was argued that making such fictional items illegal hurt, rather than helped, children; because it took away non-harmful outlets for the desires.

The thing is that the catharsis theory, that is, the theory that providing harmless "outlets" is a way to manage the desire, is not supported by any evidence. On the other hand, Patrick Galbraith has done work with Japanese fictional child porn communities and found that the communities tend to strike a very powerful distinction between real desire and fictional desire. They just don't view real children in the same "space", mentally, as fictional children in pornographic comic books.