Do you know how much porn there is of the My Little Pony characters? Tons
Do you know how much of an epidemic there is of cartoon watchers going out and fucking ponies? Somewhere between null and zilch... Maybe one or two extreme cases, but that's around the same amount of people who watch Super Hero movies and try to jump off the roof in order to fly.
This is a slippery slope fallacy if I ever saw it.
Heck, if anything we've seen that restrictions on porn actually leads to increased instances of sexual assault, in the same way a crackdown on drugs just leads to more deaths from overdoses.
If letting some sicko have fake images of pretend children saves even one real child from being viciously exploited, I think it's worth it.
It's not ideal and yeah, it makes the skin of any sane person crawl... Ideally we should be out curing pedophiles of their sexual urges entirely, but since we don't have a way to do that why let perfect be the enemy of good? I mean what other ideas do we have? Cause "To Catch A Predator" may have been good television, but even that had ethical concerns ending in lawsuits lost and suicides performed, and castrated everyone convicted isn't exactly 8th Amendment friendly... and even then that prevents repeat offenses, not initial offenses. (Prevention > Cure)
Now all this aside, we do need to look at this on a case by case basis. If real children are being used to model for the AI or fake images are used as a form of blackmail (Think "Revenge Porn", but way, way worse), then cuffs need to be slapped on people.