Letting a child on the internet should be considered abuse in the same way as letting them into a strip club or drug-taking establishment would be.
There must be ways to allow children to learn to use computers and information technologies without letting them anywhere near the internet. It's just extreme laziness on our part that we don't bother trying.
But, of course, the children argument is the real strawman here. Nobody is interested in the above solution because this is really about preventing adults from using the internet as they currently do.
Don't get me wrong, I think a lot of the stuff the internet enables is abhorrent and harmful but let's not throw out the baby with the bathwater here.