I'm with you all the way on this. Your views are pretty far from the mainstream of US public opinion, though.

selling their own old pictures when the child becomes adult could become legal

That view in particular would make you a pariah in many social circles.

• if it is proven that the pictures do not increase the crime.

All I want is the absence of proof that it increases the crime. Since Diamond has evidence that it decreases the crime, that's pretty clear.