On Tuesday, we had a solemn commemoration of the liberation of Auschwitz 70 years ago on January 27. We use the date to mark all the particular victims of the Holocaust and other appalling crimes by humans against fellow human beings.

What saddens me most is that while the intensity of the mass murder remains unequalled in both its intensity and its ruthlessness, the event is not unique. In Cambodia in the 1970s, along with Rwanda and Yugoslavia in the 1990s, we saw similar hatred and death. Unfortunately for most of us, the only enduring legacy is the news media euphemism “ethnic cleansing”.

We must not forget that the Jews were not the only victims of the extermination camps; homosexuals, political opponents, those with learning difficulties, and gypsies were also subject to the same inhuman treatment and brutal murders.

However, it is the way that Nazis turned every part of civilised society to this goal of killing Jews not just in Germany, but in any other part of the world where they were able to do so. Science and engineering were distorted to find cost effective ways of killing. Psychology was used to find ways that did not drive the murderers themselves to despair. Logistics were perfected to transport millions of people to incarceration or death.

The Nazis rewrote laws and manipulated the entire legal system to deny citizens of their very existence.

You may ask why this still matters? Some may even console themselves by saying that these events were committed elsewhere, by foreigners, and at a different time.

In this thinking, all we need to do is be vigilant for the ‘bad apples’, the few genuinely evil people, and we will be safe.

The most horrifying lesson from Holocaust Day is that each of us could end up aiding and abetting such crimes. In many occupied countries, as well as Germany and Austria, ordinary citizens went along with the deportations and the enforcement of rules. Were all the Vichy Police in France who forced people on the trains to the death camps really die-hard fascists? That is unlikely. We mock the cliché “I was only obeying orders” but it is our usual desire to conform that makes us vulnerable. In the 1970s, there was an experiment, taking ordinary students and asking some to act as warders, the others as prisoners, in a mocked-up jail. The experiment had to be stopped within a few days. No one told the guards to become sadists, but they did. There is no easy solution to this threat, but we all have a part to play. To start, we must challenge stereotypes and reject attempts to demonise and dehumanise whole groups. No one said being free was easy.