Short story. A major type of porn is cartoon porn based on current cartoons kids are watching. My 13 year old son was searching for sites on Pokeman. He found one which had cartoons on it. Now, we monitor our childern closely. His only access to the internet is a computer at my office where he sits with people around him including myself.
So, much to his surprise he runs one of the cartoons on a site that has no indication it has porn and to use his words "It was gross". He saw more than he wanted to see.
If a filter can keep that type of stuff from happening then I'm all for it. Its no different than placing covers over the front of porn magazines.
My guess is that it would prevent some, but not all, of that.