Every Shabbat at Highgate Synagogue, a member of the congregation has marked the 70 Days For 70 Years project by speaking about an essay from the compilation from which they have drawn inspiration, and in memory of a specific victim of the Holocaust. Recently, I made my speech in honour of Rachel Van Dam, who died in Sobibor concentration campat the age of 66. My speech came two weeks after the Charlie Hebdo shootings in France.

I find it incredibly difficult to engage with the details of the Holocaust. I know the history. I obviously know what happened. But I haven't been to Yad Vashem, I haven't visited the camps, I haven't heard personal testimonies or gone to talks by the victims. I find the full horrors of what happened difficult to compute. I told the congregation that my default position has been to build a set of values that I hold dear, often drawn from the darkest time in our history.

So it was ironic that I chose an essay called "The Nazis'' as the inspiration for my talk. It came from a book of the same name by Laurence Rees and is about the psychology of the typical Nazi officer. It reinforces a stark fact that we all too often forget. That "the extermination of the Jews was not somehow imposed by a few mad people upon an unwilling Europe."

On the contrary, the scene was set. Virulent antisemitism prevailed, leading to former members of SS units declaring that they were not acting under orders, nor had they been brainwashed by propaganda. It was just perfectly reasonable to kill Jews. After all, Jews were to blame for Germany losing the First World War, Jews wanted to take over the world, Jews conspired from within against Germany's enemies; Jews were the traitors and Jews were evil. Indeed, at Auschwitz, there is little evidence of guards being prosecuted for refusing to take part in the killings. We can kid ourselves all we want, but the murder of six million was a collective enterprise, owned by thousands of people who made their own decisions.

The essay concluded with the following observation: "Human behaviour is fragile and unpredictable, and often at the mercy of the situation." Rees implies that the capacity of humans to carry out extreme and horrific actions can be determined by the macro environment they find themselves operating in. In essence, he suggests that this was mob culture on a grand scale. He then observed that if individuals can be buffeted around by the situation, then groups of human beings working together can create better cultures, which in turn can help individuals to behave more virtuously.

We must be at the heart of bringing people together

This well-known part of Holocaust history had, yet again, struck a real chord with me. I reminded the congregation that only a week earlier, our rabbi (Rabbi Nicky Liss) had asked us what seemed like a straightforward question. He'd said: "How many of you are Je Suis Charlie, and how many of you are not?" As it happened, my position on that very issue had shifted as events in France unfolded. I was unconvinced that we were even asking ourselves the right question. It seemed all too easy to be Je Suis Charlie. Was it as easy to ignore the insidious attempt by militant secularists and the Far Right to hijack this powerful statement? I'd listened to words of caution from Rabbi Sacks and other faith leaders about the need for communities to pull together, and suddenly the question seemed a good deal more complicated.

At a time when we again have evil in our midst, when Islamic extremists are intent on bringing brutality to the world, on a scale of terror too enormous to comprehend, the Jewish community must be at the heart of bringing decent, moderate people together. We must set a macro environment of tolerance and respect. While we must work together to defeat evil, we must also speak out against those within our ranks who teach their communities to demonise literally millions of people, tarnishing them all with one brush of fanaticism.

We must be a light unto the nations - by creating situations where individuals become groups - groups who stand together and protect, at all costs, the common values we must hold dear.