The thing is, if you want to prevent your children from accessing sites you'd prefer them not to without accompanying them in the future... there's been commercial solutions to that almost since the first porn site existed. Net Nanny's been around almost as long as I've been alive. Combine that with ensuring that your child's computer is in a public place, not their bedroom.
Frankly, if people are going to be exposed to said imagery at some point, they probably need to be educated about it. And not just about porn - about people with racist and bigoted views, about the news they'll read about someone committing a school shooting or a bombing.
There's no way we're ever going to convince people on the Internet to self-categorise and warn people about what they're going to come across. The only option is to supervise your child's use of the Internet (and other media, tbh) while you try to prepare them for what they're going to come across.
Frankly, if people are going to be exposed to said imagery at some point, they probably need to be educated about it. And not just about porn - about people with racist and bigoted views, about the news they'll read about someone committing a school shooting or a bombing.
There's no way we're ever going to convince people on the Internet to self-categorise and warn people about what they're going to come across. The only option is to supervise your child's use of the Internet (and other media, tbh) while you try to prepare them for what they're going to come across.