"Even the antis will say that the source of harm to little girls from sex with adult men is from when they find out when they're older that it's wrong; so society simply needs to not say that it's wrong, and then there won't be a problem."
A half-truth again. Such a thing might really be said to children -- sex with adults is not necessarily wrong -- but it is possible only when a few centuries have passed, and it would then be based on the equality of children, not on their subjection.
Society is not going backwards. Sexual fantasies and fantasies of the past are a different thing.