Well Japan quite literally has the lowest crime rate in the world, even when their media is so extreme, my guess is that it externalizes all the sick thoughts that humans realistically have and this might let off a considerable amount of steam. I've also noticed that the line between extreme media and media for children is set very well in Japan, but in other countries with degenerate media, it often finds itself slowly melting into media meant for the general audience, which includes children.