Yeah... Well... I can understand it, but not from any viewpoint that would let you sleep better at night.

Well, can you tell me then. I've gone through some dark times, but I don't think I ever could hurt someone I don't know.

Well, obviously you have your Psychopaths and Sociopaths who enjoy hurting others (To varying degrees) but leaving them aside the easiest way to get a regular person to kill/harm another human is to turn them into an agent. The way it works for the normal person is, take someone like you for example- They wouldn't ever want to hurt someone and probably could never do it. But then that changes when they are no longer acting independently and are acting as an Agent for another person, typically an authority figure. They are no longer responsible for their actions as they are working/acting [i]for[/i] the authority figure and so the normal moral checks and balances are suddenly a lot less important. It's the 'just following orders' defence that gets mocked so openly by people who think they would act differently in the same situation. Because they are just following orders, typically to avoid punishment or censure for not following those orders all kinds of stuff can happen that if you asked that same person to just do for fun they'd probably look horrified. Like the guards at Nazí camps, they weren't all vicious psychopaths and yet they all took part in the massacre of prisoners and civilians. Or My Lai (Spelling) I doubt the whole platoon were deranged mass murderers but acting as a group and following the orders of a crazy officer, they killed hundreds of women and children. Three of them tried to stop it, but were called 'traitors' by several congressmen/higher ups. Calley wasn't following orders, but he gave orders to his platoon. I apologise if any of this is slightly [i]incoherent[/i] it's quite late (5am) so I might have missed a few bits. But basically there are a lot of situations which can lead ordinary people to do atrocious things.