One person's filth is another's erotic art.
Once government start banning or controlling this, they won't stop. Eventually, you would only end up with government filtered content because the governments would be under so much pressure for the next moral issue to hit society. Ban junk food sites, ban you tube because there's some scary stuff on there about sharpening pencils with a craft knife...
In essence, the proposal won't work. How do you know it's porn firstly ? The originator has to classify it. What if they don't ? Do you say only streams with a classification are allowed ? You will really throw the baby out with the bath water then.