One of the problems inherent in dealing with atrocities is the fact that historians tend to be somewhat cut off from the normal elements of human society. Historians look for reasons and for reasonable interpretations. Unfortunately what we actually see, when we look impartially at the evidence, is very simple: most people, at all times and in all places, will believe what they are told and do what they are told. We're a group species and we're hardwired to play follow-the-leader and do what those around us are doing. Ordinary people do great evil simply because all their neighbors are doing great evil too. There is little value in breaking out subtle differences between participants. What is crucial is we realize how fragile and flimsy civilization is, and how easily it is torn apart by unscrupulous demagogues. Sadly, we never learn this lesson, which is why we repeat the same mistakes and create the same horrors over and over and over again.