Explicit pornography is so easy to find that little kids in libraries find it all the time. Librarians (almost all rabid leftists) fight porn filters as though they would kill us all. Any home with internet and no filters (and kids aren't bad at figuring out how to get around a lot of filters) can be a porn emporium.
Cable TV is in millions of homes. Any kid who turns it on can see explicit stuff pretty easily.
And to say that parents should be able to prevent kids from seeing porn is very weak. I guess all the TVs could be tossed, and no internet connection, and parents could make sure that all the friends their kids have also have no TVs or internet.