Shame … It has become associated with online mobs and prudishness, but shame can be a powerful tool to change our culture and hold governments and corporations to account.

“First holiday snap!” read the faux-cheery caption on the picture Laura Muldoon posted, featuring a bunch of young men on a plane, one flipping the V sign and another giving the finger to the camera.

Muldoon, who was flying on Ryanair with her girlfriend to Spain for a wedding, tweeted that she had just been called a “miserable bitch”, a “dyke” and a “lesbo” after complaining about rowdy behaviour from fellow passengers. The picture went viral and was picked up by newspapers. Before long, some of the alleged perpetrators had been identified publicly, their social media feeds combed for incriminating details, their mothers tracked down for comment – named and shamed, along with the airline whose staff Muldoon accused of failing to intervene sufficiently.

Shame has a bad reputation these days, redolent of pitchfork-wielding online mobs at worst and starchy prudishness at best. It is not a weapon to be used lightly, perhaps especially not on social media – where, as Jon Ronson argued in his book So You’ve Been Publicly Shamed?, brutal pile-ons can easily escalate out of all proportion to the original offence caused by one crass remark.

Yet shame has a rather longer and more nuanced history as an important means of society holding individuals accountable for their treatment of others. This may help explain why Muldoon’s response to a potentially ugly situation won widespread plaudits. Used constructively, can shame still be a powerful means of curbing antisocial behaviour in public?

“People often say they disagree with shaming, but what they really disagree with is the norm that is being enforced or the form that shaming is taking or the degree to which the shaming occurs,” says Jennifer Jacquet, an academic and the author of Is Shame Necessary? New Uses for an Old Tool. “These are separate issues.” To put it another way, like most tools, it can be used for good or evil, depending on the end to which it is employed.

After all, it is an absence of shame that allows Donald Trump to say with a straight face that “nobody respects women more” than he does, even as credible allegations of sexual assault stack up around him. The power of shamelessness in politics is that it eliminates the need to apologise or explain; awkward facts or glaring contradictions are simply ignored. It helps explain how Boris Johnson, a suspiciously late convert to Brexit who was in two minds about it until the last minute, can now unblinkingly present himself as the only true believer in the Tory leadership race. It is what allows Nigel Farage to talk one minute about how he will “pick up a rifle” if Brexit doesn’t happen and insist the next that others shouldn’t use inflammatory language.

As Trump has demonstrated, politicians who refuse to feel bad when they are caught doing something in their private lives that they shouldn’t be can be surprisingly hard to hold to account. Perhaps Diane Abbott’s mistake, when a photograph of her drinking from a can of M&S mojito on the Overground was posted on social media, was to express regret for breaching the rules, rather than shrugging and daring anyone to care about something half of London must have done at least once.

‘It is an absence of shame that allows Donald Trump to say with a straight face that “nobody respects women more” than he does.’ Photograph: UPI/Barcroft Media

Shame differs from guilt, the private torture of knowing we have done wrong, in that it requires an audience. To feel shamed is to be made to feel unworthy of our peers, a feeling humans will go to great lengths to avoid. That feeling is triggered by the disapproval or mockery of others. Psychopaths don’t feel shame because they don’t care what other people think. Conversely, groups who are already mocked or marginalised in society may be more vulnerable to shaming than high-status individuals because they have less goodwill to lose. A working-class woman with several children by different fathers and a boyfriend only slightly older than her eldest daughter might find herself judged more harshly than Johnson was if the police were called to a domestic argument at her partner’s home. A black presidential candidate might not be able to brush off stories about sleeping with a pornographic actor after his wife had just given birth as easily as Trump did. Shame has a history of being wielded against people who don’t deserve it – and there is nothing useful or constructive about the shame that discourages rape victims from going to court or drives teenage girls to despair in front of their bedroom mirrors because their bodies don’t meet an Instagram ideal.

Yet what makes shame so valuable as a tool is that it is one of the few the weak can use against the strong, according to Jacquet, a professor of environmental studies at New York University who became interested in shame as a means of bringing pressure to bear on environmental problems.

“Shaming is still the main way we enforce norms about human rights – by exposing countries or institutions that are using slave labour or child labour or horrific working conditions,” she says. “In many cases, we have to rely on social exposure because there is not a strong formal governance system in place that protects these workers. So we shame the brands or the industries to affect end consumers, with the hope that it translates to better practices on the production side.”

‘Perhaps Diane Abbott’s mistake was to express regret for breaching the rules, rather than shrugging and daring anyone to care.’ Photograph: Victoria Jones/PA

Since her research focuses on problems that cross national borders, Jacquet is particularly interested in the fact that shame can quickly be scaled up from the individual to the national level. “While guilt is personal, I argue shame is unique because it can be used against institutions – governments, corporations – and they often change their behaviour in response to the threat of shame because they are concerned with reputation.”

The caveat, however, is that we appear to have entered a period in politics in which the electoral rewards for shamelessness outweigh the reputational damage it causes.

If the tipping point in the US came in 2016, when it emerged that a tape of Trump bragging about grabbing women “by the pussy” wasn’t going to stop him entering the White House, then Britain’s low-water mark may have been the Brexit referendum.

In 2016, the Vote Leave campaign came under ferocious criticism for its misleading slogan that leaving the EU would free up £350m a week for the NHS, as well as the equally misleading suggestion that Turkey was about to join the EU and millions of Turks might soon come to Britain to work. But if the intention was to embarrass the campaign into backing down, it didn’t work. Instead, Vote Leave pushed its disputed slogans even harder, banking on the fact that a public row would serve only to get its preferred talking points up in lights.

And it worked. Whatever broke loose inside British politics at that point has only been further fractured by Theresa May’s struggle to hold together a fractious Tory coalition of leavers and remainers throughout a hung parliament, which effectively meant turning a blind eye to some shameless behaviour.

Cabinet ministers became unsackable in all but exceptional circumstances, with what might normally have been resigning issues – flagrant leaking, public breaches of collective responsibility, poor policy judgments – going unpunished. Two Tory MPs who had had the whip suspended over allegations of sexual misconduct found it quietly restored ahead of crucial votes. Established norms of political campaigning and conduct have been stretched to the limits by trying and failing to deliver Brexit. Judging by some of the more wildly unrealistic Brexit promises made during the Tory leadership race, they have yet to be restored.

There are signs British politics has not reached Trump-style levels of shamelessness just yet. It is telling that while the US president tends to come out swinging when in trouble, Johnson has shown a tendency to avoid broadcast interviews and debates. Instead, he has sent a string of proxies to field the inevitable awkward questions about why he once offered to provide a friend with the address of a journalist that friend wanted beaten up or how many children he has. As the BBC journalist Emma Barnett said when raising these points with the MP Johnny Mercer, one of Johnson’s supporters, the concern isn’t about his private life per se so much as his persistent reluctance to tell the truth about it.

Ducking questions may not be particularly admirable, but it isn’t the behaviour of a defiantly unembarrassed person, either. Colleagues say Johnson has been genuinely wounded by accusations of racism and homophobia, based on language used in past newspaper columns, in recent weeks. He is also reportedly more troubled by the public collapse of his marriage than he lets on. Then there is the late-night row with his partner, Carrie Symonds, which suggests he may be feeling under pressure.

“I think maybe, unlike Trump, with Boris, there’s an inner turmoil about it all,” says his biographer, Sonia Purnell, who points out in her book Just Boris that, for all his repeated philandering, he has always craved the approval of his estranged wife, Marina Wheeler. “In some ways, you could say it’s worse because he knows what he’s doing and still doing it.” But it also suggests that Johnson is not so far down a Trumpian road that he couldn’t be embarrassed into turning back.

Besides, Jacquet argues, the value of shaming can lie not in its ability to make an individual change their behaviour, but in reminding wider society why that behaviour matters. She cites the case of Walter Palmer, the trophy-hunting American dentist who was condemned for sharing a picture on social media of himself standing over the corpse of a lion: “He was shamed disproportionately and, as far as we know, it probably made very little difference in his behaviour. But that moment was very interesting to me because there was a lot more disdain for trophy hunting than I had realised. So, yes, it’s possible to shame the shameless. It’s possible that it even matters in establishing new behaviours.”

Once upon a time, fear of having to publicly identify herself as a lesbian might have shamed a woman into keeping quiet about any prejudice she experienced on a flight. If nothing else, it says something about how times have changed that shame now flows the other way.

By Gaby Hinsliff, Tue 2 Jul 2019 13.52 BST