Even if you can’t reliably control it, if you make a tool that generates CSAM you’ve made a CSAM generator. You have a moral responsibility to either make your tool unavailable, or figure out how to control it.
There's a line we have to define that I don't think really exists yet, nor is it supported by our current mental frameworks. To that end, I think it's just more sensible to simply forbid it in this context without attempting to ground it. I don't think there's any reason to rationalize it at all.
you going to ban all artsy software ever because a bad actor has or can use it to do bad actor things?