the fact that he has obviously learnt how to remove the controls and hide his tracks means he will look at this stuff whether you like it or not - trying to stop him will just cause conflict - and wont stop him - he will find a way.
all you can do is educate him about it - as ummm says, thats its acting, its not real and not to expect that kind of thing with any girlfriends he has in the future, and that real women tend not to like being spoken to as though in a porn film etc.