A word of our time is “normalisation”. It warns of the error of treating as normal that which should instead be shunned. It has in its sights the xenophobic, populist and racist right embodied by Donald Trump and his henchmen, as well as their European and British allies. It says that these people should not be afforded the usual courtesies of civilised, democratic life but should instead be left out in the cold.

All my instincts are with the anti-normalisers. Indeed, when it comes to Trump, I got there early, writing in this slot even before he’d sworn the oath of office: “Don’t treat Donald Trump as if he’s a normal president. He’s not.” I’d happily extend that rule to the likes of Steve Bannon, briefly Trump’s chief strategist, now keen to pose as an impresario of the populist international, lending his semi-celebrity to far rightists from Italy’s Matteo Salvini to Britain’s own Stephen Yaxley-Lennon, who styles himself “Tommy Robinson”.

So my first impulse is to side with those outraged by the invitations recently extended to Bannon by the New Yorker or the Economist (the former cancelled under pressure, the latter went ahead). Similarly, I was as shocked as anyone else to see the original title – now changed – for an upcoming debate at London’s Conway Hall, featuring Trevor Phillips, Claire Fox, David Aaronovitch and the academic Matthew Goodwin: “Is rising ethnic diversity a threat to the west?”.

The objections are familiar. In the Bannon case, those two great magazines were not only granting a platform to a white nationalist whose Breitbart site has long peddled multiple shades of bigotry and misogyny. They were lending him the prestige of their platform, dignifying his ideas with their own good name, thereby granting those ideas a mainstream legitimacy they should be denied.

It’s no good simply crying free speech or denouncing censorship. Neither the Economist nor the New Yorker would open its doors to the Imperial Wizard of the Ku Klux Klan or the Holocaust-denying David Irving, so we know they draw the line somewhere. The only question is where.

The reason they would keep out the Klan or Irving is clear if apparently paradoxical. Tolerant societies can tolerate everything except extreme intolerance. Liberal democracy is allowed, or even obliged, to repel those who would, given half a chance, use the norms of liberal democracy to destroy it.To quote Andrew McLaughlin, a technologist who was invited to that same Economist festival and who protested against Bannon’s inclusion: “Treating racist extremists as pariahs is not just an expression of our revulsion at their views; it is a necessary tactic in defending our liberal democratic order against those who aim to gain power within our systems only to replace them with something horrific.”

Facebook Twitter Pinterest Steve Bannon (right) on ITV’s Good Morning Britain in July. Photograph: Ken McKay/ITV/Rex/Shutterstock

That is the case against normalisation. Don’t normalise people like Bannon, don’t normalise the idea – long a staple of white supremacist talk – that ethnic diversity is a threat to western civilisation. All very simple, right?

It should be, and yet two aspects of the current landscape have forced me to see that these questions are knottier than we might like. The first relates to technology and involves a pragmatic recognition of reality. In the good old days of “no platform” in the 1970s and 1980s, the practical goal of denying a racist a platform was plausible. If universities, publishers and the media agreed to shun, say, Irving, then Irving’s message would be all but unheard, confined to a few poorly produced magazines and hand-stencilled newsletters exchanged in dodgy pubs. Today, you might try to keep Yaxley-Lennon off the airwaves or a debate stage, but you could not deny him a platform: the Tommy Robinson Facebook page has more than 950,000 followers.

“The internet has fundamentally undermined ‘no platform’ as a tactic,” Joe Mulhall of the anti-extremist group Hope Not Hate told me. “In the traditional sense, it doesn’t work anymore.” Every ragtag racist with a smartphone has a megaphone within easy reach, and there’s little society’s gatekeepers can do about it.Which brings us to the second challenge to the “no platform” tactic of old. The favourite refrain of every populist xenophobe from Luton to Leipzig, from Warsaw to Wisconsin? It is that they are gagged, silenced by a distant political, cultural and media establishment – one that refuses even to listen to the left behind and the left out, one that holds ordinary people in contempt for feeling anxious about immigration and what Goodwin calls “cultural displacement”.

This is why “free speech” has become the single, catch-all banner under which an array of white supremacists and Islamophobes can now march, all claiming the same victimhood: that they are forbidden from voicing the pain of those betrayed by a liberal elite that imposed multiculturalism and immigration on mainly white communities in Britain, Europe and America and that now refuses even to talk about it.

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Which means there’s a risk that every time you disinvite Bannon or change the wording of a motion, you’re playing into the hands of the racist right, inadvertently confirming their poisonous narrative. Your intentions might be benign – to deny the right a platform – but the consequences could be the very opposite, strengthening the right by handing them sweet vindication.

Mulhall says they’ve been debating this inside Hope Not Hate, aware that the no-platform tactic risks gifting bigots the very martyred ostracism they crave. But, he notes, they’ll claim that anyway, even if you invite them in and give them a seat at the table. Witness Yaxley-Lennon’s “gagged” shtick, even though his CV boasts appearances on Newsnight, Today and the Big Questions, as well as a Channel Four documentary on his daily life and a turn at the Oxford Union.

The point here is that the struggle against normalisation is not quite as clear-cut as some of its most righteous warriors would have you believe. One rule of thumb might be useful though. If you give space to the far right, then ask yourself if you’re interrogating them – or echoing them. The flaw in that Conway Hall debate was a motion that took a racist canard as its starting point. Similarly, a Newsnight showed a graphic of “Tommy Robinson” with tape across his mouth, implicitly advancing his claim to have been silenced.

Sometimes a society has to hear even those views it finds repellent. But it should only do so with caution, care – and with its eyes wide open.

• Jonathan Freedland is a Guardian columnist