Environment can cause epidemics of evil

"You don't need a motive," Zimbardo said. "All you really need is a situation [or an ideology?] that facilitates moving across that line of good and evil." 

"What's more, a person's anonymity can be induced by acting in an anonymity-conferring environment that adds to the pleasure of destruction, vandalism and the power of being in control," Zimbardo noted.

Read the full article, "What makes good people do bad things?"