I think primarily this victimizes all those all ready victimized by the CSAM in the training material and also generally offends the collective sense of morality our society has.
As I mentioned in another comment (https://news.ycombinator.com/item?id=46503866), there are other reasons not to produce synthetic sexualised imagery of children, which I'm not qualified to talk about: and I feel this topic is too sensitive for my usual disclaimered uninformed pontificating.