Incorrect . Obscene material can be restricted in terms of its distribution and advertising. It is not an excuse to make it illegal to possess or distribute privately. This is why things like porn and vibrators are illegal to sell in stores in Texas, but you can still order it online.
The reason why child porn is illegal completely - not just restricted in its advertising and distribution - is because it's production necessarily involve abuse of actual children.
https://en.m.wikipedia.org/wiki/Legal_status_of_fictional_po...
> In response to Ashcroft v. Free Speech Coalition, Congress passed the PROTECT Act of 2003 (also dubbed the Amber Alert Law) which was signed into law on April 30, 2003, by President George W. Bush.[126] The PROTECT Act adjusted its language to meet the parameters of the Miller, Ferber, and Ashcroft decisions. The Act was careful to separate cases of virtual pornography depicting minors into two different categories of law: child pornography law and obscenity law. In regards to child pornography law, the Act modified the previous wording of "appears to be a minor" with "indistinguishable from that of a minor" phrasing. This definition does not apply to depictions that are drawings, cartoons, sculptures, or paintings depicting minors or adults.
Now, there is an argument that if the fictional content is indistinguishable from real abuse, it may be illegal. But that could probably be circumvented by providing the inputs and seed to generate the image, rather than the image itself.
I'm not super motivated to defend AI generated child porn, but the notion of banning it introduces ambiguity. Actual child abuse material can be identified because the people involved were born on a specific date and so whether or not it's illegal has a clear threshold. But AI generated content is not so easy to distinguish. The fictional characters don't have a birth date, so whether or not it's illegal becomes a lot more subjective.