In the U.S. there was a group of radical feminists who sought to impose restrictions on the production of pornography that depicted bondage, violation of women's bodies, depictions of cruelty or demeaning treatment of women on the basis that this would lead to those who viewed such images acting out the behaviors depicted in the real world.
I'm not sure there is a clear link between these things. While it troubles me that there are people who get off on images of sexualized children, or women being beaten, I'm not sure it's appropriate to outlaw the imagery completely. Why? Because for some people it may simply remain in the realm of fantasy and prevent them from acting on such impulses. Parallel arguments have been made against video games that depict violence.
The question is this: the power we give to images and the perceived need to regulate them. I am reminded of the iconoclasms in which mosaics or altarpieces that represented Christian deities and saints were destroyed in a sweep that excluded them as graven images or false idols that confused the faithful regarding the true source of divinity. While, by contrast, in the Orthodox church, icons are viewed as conduits to the divine. These are situations where images are acknowledged for their power, but the mechanisms and potentials for good or evil are regarded differently.
Who can say what the existence of a tracing or a CGI might do in terms of real world effects? You can't stop a person's imagination from manifesting the images psychically. Does the externalization of those images really make a big difference if you are thinking in terms of pedophilia? That's the crux of the issue, and I'm not quite sure how to feel about it, although feelings of protectiveness toward one's children that would outlaw such images are completely understandable.
This is a grey area and the big issue is where/when we as a society can begin reaching into other people's heads in order to insure the safety of the collective. Where and how does one define privacy and the right to entertain one's own thoughts? I think that's what troubles chris about this.