Social media did not create informers and liars. The malicious have always manufactured denunciations and the literal-minded have always confused nuance with sin. The web is simply supercharging one of those dismal moments in history when wilful ignorance and active malice are rewarded rather than disdained.

In optimistic times, one can almost sympathise with character assassins. In Normal People, Sally Rooney has her female lead think, “cruelty does not only hurt the victim, but the perpetrator also, and maybe more deeply and more permanently”. The victim may get over it. The abuser must always live with the knowledge that they are a thug.

Rooney published Normal People in 2018 as cancel culture was turning from a sideshow into a fiery inquisitorial movement. If its perpetrators are “more deeply and more permanently hurt” than their targets, the pain does not slow the delivery of half-truths and outright falsehoods for a moment.

Rooney provides an example of how spite dresses itself in the clothes of virtue. Because she has a new novel out, she has moved into the sight lines of the rich world’s commentariat. With so much competition, how can one attention-seeker stand out? Today, there is a ready-made answer: suggest your target is racist. Even when the accusation is demonstrably false, such are the levels of fear in the “progressive” west that editors and readers will find all kinds of excuses for biting their tongues.

The Sydney Morning Herald, whose code of ethics boasts that it has “no wish to mislead” and “no interest to gratify by unsparing abuse”, ran a long attack on Rooney. Its commentator, Jessie Tu, spends an age bragging about how brave she is for defying the consensus that Rooney is an interesting writer and then announces, “Normal People should be called White People because, in Rooney’s world, people like me don’t exist. In the book, Asians are mentioned only as tourists who choke the pathways of museums in Italy. ‘I don’t know why we’re bothering with Venice – it’s just full of Asians taking pictures of everything’, one of the male characters whines.”

I was reading the novel when the piece appeared, and found the anti-Asian sentiments. They come from an odious man, Jamie. Rooney portrays him as a spoilt, sadistic rich kid. His casual racism is wholly in character. The plainest of plain stupid errors a critic can make is confusing an author with her characters. The Herald’s critic does precisely that. I read on and wondered if something more than ordinary stupidity was on display. In the book, Jamie is instantly upbraided. A man lunching with him says: “God forbid you might have to encounter an Asian person … it’s kind of racist, what you just said about Asian people.”

The apparent malice here is in the seeming assumption that an author is her characters, coupled with an omission of inconvenient evidence from the text. The charge of racism is allowed to linger so that the book can be portrayed as the story of “two white, able-bodied, beautiful straight people mulling about how hard it is to be white, able-bodied and straight” (which isn’t true either).

Occasionally, when I try to talk about progressive witch-hunts, I am met with the response that I should focus my energies on the malign actors with real power on the right. I do, and accept it is true that in England, but not in Nicola Sturgeon’s Scotland, authoritarian conservatives have more power than their progressive counterparts, and use it to purge the BBC and government bodies of any dissident voices.

Yet this is not much of a rebuke. You should be able to oppose the worst of the left and the right simultaneously. To argue that you are justified in your selective ethics because you are the moral equivalent of Boris Johnson is no argument at all.

In any event, power’s ability to harm is relative. It depends on where you stand. In most of the liberal culture industries the fear of public shaming by progressives is far greater than the fear of state punishment. It’s one thing if the shaming is justified but what follows when the denunciations are false?

These are almost impossible questions to answer today. Human resources departments and police forces would never give researchers wanting to separate the true from the false complaints access to their files. However, the opened archives of the dictatorial states of the 20th century provide clues to the consequences of allowing denunciation to flourish without regard to truth.

Historians who investigated the files of the Gestapo in Nazi Germany estimated that personal malice motivated 40% of denunciations to the secret police: wives who wanted husbands out of the way so they could be with their lovers (and vice versa) and workers taking office politics to the extreme. You hear faint echoes of this today. In the highly competitive publishing market, public political outrage can provide a cover for taking out rivals or for simple literary jealousy. In one delicious case in the United States, an author who cancelled his contemporaries for appropriating gay themes had to withdraw his own book when it was accused of appropriating the Serbian mass murders of Balkan Muslims and using them as a backdrop for a cute love story.

In the UK, many authors have noticed the silence of literary organisations, staffed by minor cultural bureaucrats. They are meant to defend writers without fear or favour but have failed to condemn the waves of death and rape threats directed at JK Rowling.

Research from Communist East Germany, covering the 44 years from the fall of Hitler in 1945 to fall of the Berlin Wall in 1989, is as suggestive. The historian Hedwig Richter wrote about how East Germans informed on one another, without being asked to, and when they had no legal obligation to snitch. Their accusations gave them the hope that the state would look kindly on them and they could “avoid potential problems and misunderstandings in the future”. That urge to please is the less dramatic but more lasting danger of heresy hunts on the left (and the right). Frightened people go along with them for fear they will be condemned as heretics if they do not. The result is a culture that appears self-confident on the surface but is sterile and conformist underneath. You don’t have to look far to find it. It is all around you.

• Nick Cohen is an Observer columnist