I think it already has, that guy who wrote the pedophilia guide and sold it on Amazon was arrested after he sent some police officers a copy of his book through the mail, across state lines or something.
This is really the only concern,
"Olof Risberg, a psychologist who works for Save the Children in Sweden, said he was concerned with illustrated sexualised images of children becoming normalised, as this means the step to accepting sexual images of actual children will get smaller. He admitted that in illustrated images there are no victims, but still insisted it is wrong to ‘expose children in a pornographic context, whether they’re illustrated or real children… but even in this case, I think the [Manga] images are unnecessary and wrong’. "
But I am more concerned with images of violence becoming normalized. Unconsenual sex with children is violence so it is a tough decision to make, I think we should err on the side of free expression though.