The claim I'm making is that they are underprotected online.
I think you are concerned about the pendulum swinging too far in the other direction but I don't think I said anything that suggests that should happen. Unless perhaps you think the current amount of protection is already the maximal amount that is useful?
Yes, and not only is it wrong (they are protected sufficiently), but giving an inch to the same moral impulses and people that resulted in them being overprotected in the real world will naturally result in them taking a mile.
The ideal number of human beings that do stupid shit and pay for it is not zero, nor can it be in any functioning society.
The onus is on the parents though, they need to monitor (to some degree) what their children are doing online. This seems trivial to me using modern Family controls on iOS or Android + maybe DNS filtering at the router level.