I am currently reading Tzvetan Todorov's classic book Facing The Extreme. It is a fascinating exploration of what happened to morals and ethics in Nazi and Soviet concentration camps. Where individual responsibility for evil lies, why some people still "do the right thing" in the face of intolerable pressure, and how easy it becomes for everyone responsible for evil to be "just doing their job".
To some extent the camps were the logical extension of totalitarianism. You gain power and influence by identifying the enemy, even the enemy within, demonise and dehumanise them, and then justify their eradication. It is all too easy to see this as something particular to the German or Soviet character, or even to excuse it on the basis of the culture and norms of The Thirties, but to do so would be dangerously complacent. Stanley Milgram's famous experiment took place in America, Guatanamo Bay is still in use, and the circumstances of Donald Trump's rise are being compared to those of Hitler.
What is striking about the evil described in Todorov's book is how ordinary it all was. Very few of the guards were sadists or psychotic in any way. The vast majority were very average people. People pretty much like you and me. People trying to get through their days, to keep their families safe, not ruffling too many feathers.
It is all too easy for us to see evil as the result of particular, malevolent, individuals. But that is not how it happens. It is lots of little actions, or inactions, by lots of people that lead to our greatest nightmares.
As I have so often said "we all have a volume control on mob rule". We need to start exercising that volume control...