The problem is that pretty much anything can have effect. With your approach you would have to ban everything to the level of people with lowest resistance. Fi

The problem is that pretty much anything can have effect. With your approach you would have to ban everything to the level of people with lowest resistance. First you ban torture videos, then murder videos, then animal slaughter, then violent porn, then violent video games, then violent movies, then all movies where gun is shot (see shooting ar-15 gave me ptsd) and you have banned all action movies. And you still can't be sure if there isn't anything even more benign which would have "an effect" on someone.