That's not quite true. I remember being part of some debates over whether cartoons of young-looking people (rarely can you accurately guess the age of a cartoon) were child porn or not, in a western company.
The legal and moral justification for banning images of child porn is that distribution encourages production, and production of it is dangerous to real children.
This is a second order effect that's already somewhat debatable (does getting rocks off to porn cause fewer paedophiles to try and sate their desires in the real world, thus lowering abuse rather than raising it?), and it's therefore not entirely clear there's a strong moral or legal justification for banning cartoons or pure text, i.e. trying to ban people imagining child porn. For all we know, if it's true that paedophilia is caused by some sort of brain condition (and why would it be false), then these things could actually be helping children rather than hurting them.
The legal and moral justification for banning images of child porn is that distribution encourages production, and production of it is dangerous to real children.
This is a second order effect that's already somewhat debatable (does getting rocks off to porn cause fewer paedophiles to try and sate their desires in the real world, thus lowering abuse rather than raising it?), and it's therefore not entirely clear there's a strong moral or legal justification for banning cartoons or pure text, i.e. trying to ban people imagining child porn. For all we know, if it's true that paedophilia is caused by some sort of brain condition (and why would it be false), then these things could actually be helping children rather than hurting them.