Point of fact: child pornography is obscene–and not covered by 1A–even if no real people are harmed. I’d have to dig up the law (I think it dates to the mid-90s), but it’s pretty broad. Lolicon may be illegal by itself, even though drawings don’t generally cause direct harm. At least one person has been convicted of obscenity for comics, albeit not lolicon. It is *likely that even AI-generated child pornography, even though it wouldn’t involve real children, would end up being ruled obscene.
Personally, I would take your position; images and depictions of child pornography that don’t involve actual minors should not be obscene and therefore illegal, regardless of how distasteful and repellent they are.