The tech companies insist that the corona pandemic of 2020 will not be a repeat of the US presidential election of 2016. With millions of lives at stake, economies collapsing and hunger spreading, they will not rake in the advertising revenue generated by fake news and Russian disinformation this time round. They are responsible corporate citizens. Or so they wish us to believe.

Early in the lockdown, YouTube and Facebook made a great fuss about removing a David Icke video in which he claimed the coronavirus wasn’t a virus but a sinister sickness spread by 5G networks. Asked about attacks on phone masts by his confederates in duncery, Icke didn’t fall over himself to condemn them. “If 5G continues and reaches where they want to take it, human life as we know it is over... so people have to make a decision.”

Facebook said it was “committed to removing misinformation which could contribute to physical harm” as it took down the interview with Icke and the London Real conspiracist site. (There’s little real about it, I should add.) YouTube said it had no truck with “conspiracy theories” and did the same.

They weren’t serious. If they had been, they would have banned Icke and his imitators. As it was, Facebook and YouTube did not say they could no longer tolerate Icke on their platforms. They gave him the aura of being a free speech martyr by removing one interview, which he gratefully exploited, then allowed him to carry on as before. At the time of writing, close to 500,000 had watched a recent Icke video entitled “Is There a Virus?” that YouTube had not taken down. Icke’s jowls bubble with suppressed fury. “They” were “redesignating” deaths from flu and from 5G waves as deaths from Covid-19, he explains. And why would “they” go to the time and trouble of doing that? Because “they” want to “destroy independent income” and impose a “massive fascistic global Orwellian control of the population”.

I can’t think of a subject more saturated with dishonesty than freedom of speech

The far left and alt-right cannot put forward a conspiracy theory without hitting on Jews. The legacies of religious, fascist and communist antisemitism are invisible forces propelling them forward to the irresistible conclusion that only one people had the occult power to fool and impoverish the whole wide world without anyone except the wised-up Icke and his kind noticing. Who are his “they”? Where can we find “them”? They are the 1%, Icke explains. Specifically, an “ultra-Zionist billionaire”.

I spoke to Google, the owner of YouTube, and asked why, if it meant what it said, it had not closed Icke down. Apparently most Icke content was still within its guidelines and would not be censored, I was told, an answer that leads us into a swamp.

I can’t think of a subject more saturated with dishonesty than freedom of speech. Opponents say it does not matter if a social media platform or a university bans speakers. Private organisations deciding for themselves who they wish to be associated with cannot be compared to state censors. They refuse to acknowledge that if a feminist academic is deemed transphobic and cannot talk in universities, there are precious few other venues open to her. Nor that many public figures are heard on social media or not heard at all. In the past decade, to cite the case of an almost forgotten figure, the far-right fop Milo Yiannopoulos was a social media celebrity feted and hated in equal measure. Twitter banned him in for leading a pile-on against a black actress, and its censorship finished him off. If Facebook and YouTube were to ban the corona conspiracists, that would be censorship too, and it is deceitful to pretend otherwise.

Alongside the pretence that censorship is not censorship is a hyperinflation in the notion of what speech should be punished for causing harm. The liberal, as distinct from the libertarian, argument is that only speech that directly incites crime should be prohibited, a demagogue whipping up anti-Muslim sentiment outside a mosque, for instance. Since the 1970s supposed “liberals” have wanted offence to be included as a harm. No one should deny that words are weapons that can hurt more than a blow. Unfortunately, no one can measure the psychic wounds that an offended person feels with the accuracy of a doctor measuring physical wounds on a victim of crime. The woolliness of their “hate speech” laws all but guarantees that they will punish the innocent.

Yet, in the case of Icke, there is no need for debates about whether the harm is real or whether it is just hurt feelings. Knuckle-dragging fantasists have physically attacked phone masts. Daniel Allington and his colleague Nayana Dhavan at King’s College London have shown that Ickean conspiracy theories pose a physical risk to public health. Conspiracists put their own lives and, crucially, the lives of those around them at risk. Because their gurus have persuaded them that health advice is a giant lie, they see no need to stay at home, wash their hands or observe social distancing. YouTube and the social media companies are complicit, because they want the audience and revenue that crank celebs bring.

They can pocket it because of a legal absurdity. Television broadcasts are regulated. Last week, Ofcom sanctioned a tiny TV station called London Live because it broadcast Icke “casting doubt on the motives behind official health advice to protect the public from the virus”. Yet it has no power to regulate YouTube when it broadcasts Icke saying that health workers and governments were responsible for deception on a supernatural scale.

Parliament should have intervened in 2016 when the extent of Russian manipulation of social media was made painfully clear. There is a stronger argument for forcing the tech companies to live by their pious words now that so many are suffering. Liberals should always defend freedom of speech. But they have no obligation to help turn their countries into morgues.

• Nick Cohen is an Observer columnist