Sure, but you could have a setting which allows sexualised content to be accessed or showed. Or just a popup when entering the stream like it already does with mature streams or whatever they're called. You can have the streams only visible to people logged in, have people put their age on the account when making it (not sure if already a thing) and not show this stuff to people under 18. Yes you can just say you're 18 but in that case the kids do it deliberately and won't just stumble upon it. Have the parents do an underage account for them. Lots of options, and yes, the parents do have responsibility as well.