The blame can be spread widely. Social media corporations, such as Twitter and Facebook, have allowed racist networks to proliferate. Recent research from Western Sydney University, looking at a decade of cyber-racism, has shown that race-hate groups are sophisticated and creative in disseminating racist propaganda to their followers online. The Gab social network and the journal Psych seem to have been set up expressly to give these elements their own unfiltered space. Online magazines such as Breitbart, and the companies that advertise through them, are complicit in presenting a glossy front to bigotry. And then comes the second tier of publicity when, even if only in outrage and disbelief, this content is shared online. This, in turn, has infected mainstream political discourse, lowering the tone a little further every day.

The racists like to couch this as a freedom of speech issue. They argue they have the right to say what they want, that the world needs more “diversity of opinion.” But do the rest of us have a duty to sit and listen to racist pseudoscience? Is society obliged to give them platforms, however much nonsense they come out with? Doesn’t it have a responsibility to protect those whose humanity and safety is threatened by the minority who seek to deny people equal rights and freedoms based on race or gender?

People once imagined that social media would somehow regulate itself, that only the truth would survive in the marketplace of ideas. If the only racists left in society were uneducated thugs at the fringes of everyday life, what harm could they pose?