Tagging certain subjects of artistic expression as illegal reeks of thought police, particularly when the work is unmistakably fictional.
As for actual CP, definitely against. I think the issue is a bit more complicated than "anything under 18 is no good," but I don't have a problem with it. A lot of people can be exploited just as easily when over 18 as under. On the other hand, people have to be responsible for themselves at some point, and I guess 18 is as good a date as any. Though maybe there should be a test or something instead . . . .
I just thought of something. if age of consent varies from place to place, wouldn't that affect the meaning of CP? is it legal to look at naked 15yrs old in hick land where age of concent is 14, but not ok where 18 is the law?