One of the striking things in the study of perpetrators is how they live with themselves morally. It's not that difficult because this really isn't a moral issue for them. They've removed the victims from their universe of moral obligation. What they're doing to the victims isn't really a moral problem because the victim's not part of their moral universe in the way that for some of us a bug or an insect isn't. Killing it is just not a moral problem for us because we don't feel that moral obligation.