You don’t prevent it, simple. Adding invasive privacy measures that apply to all adults won’t stop the kid who wants to find porn and show it to other kids on his phone. We found ways around the content blockers at school all the time.

Extreme porn can be found too easily. It wasn't like that when I was a kid. There were no ways around it. We simply could not even think of all the disgusting fetishes that are only a few clicks away nowadays.