Violence in films and games?
There have been a long debate on whether seeing violence in films and games (where no actual violence towards people or animals has happened) would make "impressionable" people more likely to commit acts of violence. So far, there has been no evidence that this is true -- except questionable studies that looks at people that have committed violence and see that they have seen such films and played such games and concluded this is why they did what they did without considering other possible causes. The implication might very well be the inverse.
So simply assuming that watching AI-generated child porn would make people more likely to commit real-life abuse is questionable, and making laws on such an assumption even more so. It could even be that "evil desires" could be sated by AI-generated images. After all, the number of voyuer cases dropped after porn became legal.