The propaganda machine portrays the victim group as less than human. In Rwanda, the Hutus called their Tutsi neighbors 'cockroaches.' In Cambodia, the Khmer Rouge said their victims were "worms." To the Nazis, Jews were "vermin."
Dehumanization is the most powerful psychological tool used in all mass murder and genocides, Zimbardo said. "Dehumanization blurs your vision. You look at these people and you do not see them as human."
Instead, the enemy is treated as a germ -- as something to eradicate, or else face the threat of infection.
"Purification is at the heart of genocide," said Harvard's Lifton. "In that purification ... [the killers] are healing."
Recently discovered photos show Nazi officers at a retreat near Auschwitz relaxing as though they are taking a break from a routine job, not an extermination factory. "In order to carry out the function of killing, one must instill in that environment a sense of ordinariness," said Lifton.
At least nothing like that goes on here in modern America...or does it?