The psychology of evil

Philip Zimbardo, who led the 1971 Stanford Prison Experiment, gave an interesting talk on the nature of good and evil. In relation to moral development, how do certain situations seduce ordinary people to perform actions that they recognize as immoral? If we all have the capacity for evil, why do some become a reality and some not?

How and why do the photographs of Abu Ghraib prisoners acquire emotional and moral relevance? Please share what you think of Zimbardo's arguments!