Fascist ideology is by its nature incoherent and contradictory. It bundles together all sorts of fears, prejudices, beliefs, myths, symbols, images and rhetoric around a simple and brutal impulse: a desire for absolute dominance, hierarchy and racial purity. In recent years, white supremacist terrorism across the world has targeted Muslims, black people, Jews, Sikhs, Roma, immigrants and leftists. The perpetrators are often misogynists. Fascism has always followed this logic. What is new, however, is the way in which the rest of us are being made complicit, on a mass scale, in furthering its aims.

Far-right terrorist ‘manifestos’, like the one apparently published by one of the Christchurch shooters, are a kind of Rorschach test, inviting the reader to finish the job by finding meaning in the incoherent and contradictory ideas it contains. An act of mass murder is turned into a global spectacle by the use of real-time social media networks. Traditional media organisations and individuals online are drawn into repeating, arguing over and sharing the claims and images made by the perpetrator.

The central message of the manifesto – a call to genocidal white supremacism – travels in two directions. One is to pull mainstream political debate to the right and make existing divisions worse. The other is to draw people into the online subcultures in which far-right ideas thrive: the jokes, memes and conspiracy theories set up an enclosed system of meaning, where challenges from outside merely reinforce its apparent truth.

What could stop this? The first thing should be to pull the brake on the particular way in which these images and ideas are able to circulate via global networks of communication. Twitter, Facebook and Google have created social resources that many of us now find indispensable. They have made our emotional engagement – our interior lives – the basis on which they try to make profits. At the same time they largely refuse to put in place structures – editorial oversight, forms of democratic accountability – that would allow us at least some degree of control over them. We should own them, and have the power to take collective decisions about the way in which they operate. In the meantime, we need strategies to help young people – though not only young people – develop the critical thinking tools necessary for negotiating this world.

The second is to recognise that although technology can make things worse, it is not the cause of terrorism. Far right politics is parasitical on the mainstream. It has little original content of its own, but holds up a distorted mirror to more general failures and divisions. It takes the racism and the resentment that are already present in society and tries to mobilise them to ever more extreme ends. White supremacist terrorists target the people that white majority societies have already made marginal in one way or another, through historical oppression, economic injustice or current conflicts. It should not be a surprise that Muslims are so frequently the target of far-right violence in the West, when anti-Muslim attitudes are widespread among the populations of those countries, and voiced across a broad range of mainstream media. Or that Jews remain central to the far-right worldview when conspiracy theories about Jewish wealth and power persist elsewhere. It is legitimate to ask what role mainstream prejudices have in raising the risk of far-right terrorism, but it is also important to remember that isn’t the only reason to oppose them. We should oppose these prejudices because they are – in and of themselves – an appalling way to treat people.