That is its own necessity. They are at a place, in terms of their environment, character, moral mindset, and predilections, that torturing and raping for fun i

That is its own necessity. They are at a place, in terms of their environment, character, moral mindset, and predilections, that torturing and raping for fun is preferable (controlling for other factors). This kind of behavior has had a strong appeal throughout history to many of those with the strength to carry it out without any real risk to themselves. See Jack London's "The Sea Wolf" for a great portrayal of the conflict between this mindset and our own. It's player-killing in video games in the real world and the only effective way to respond is with greater force.