This is like telling someone to "stop liking rock music" or "stop enjoying ice cream." People don't decide what their preferences are, they just have them. If we can give pedophiles a way to release those urges without harming children that should be a good thing. Well not good, but positive in the relative sense at least.
That is not required. Especially in the larger models like a DALLE-3 it can combine concepts even without being directly trained on it. The one they had in the showcase for DALLE-2 was a chair shaped like an avocado. It knows what a chair is and it knows what an avocado is, so it can combine them. So it can know "this is what a naked human looks like" and "this is what a human child looks like" and could combine them without having ever seen CSAM.