To the remainer, and even to the neutral, our current politics contains a big mystery. Put simply, where is the sentiment we hoped to call regrexit? Where is the collective outbreak of buyer’s remorse? After all, the evidence that Brexit will be the greatest error in our national history since Munich is piling up. It’s not just that a process the leavers used to say would be quick and easy is proving to be long and torturously difficult, or that the European economies are growing while ours is sluggish. It’s more fundamental than that.

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It’s the fact that ending free movement will deprive our hospitals of nurses, our old-age homes of care workers and our farms of essential workers: recruitment of EU nurses is already down 96%, while farmers are already warning of food rotting in the fields.

It’s the contradictions, which are legion. We did this supposedly to stop sending money to the EU, yet now we’re negotiating over how many tens of billions we’ll pay into Brussels coffers (this time getting nothing in return). We did this to make parliament supreme once more, yet now Brexit necessitates a withdrawal bill that would see a massive shift of power away from MPs, as the executive grabs enough unchecked authority to make a Tudor king blush.

The Brexiteers tacitly concede this reality through their quiet dropping of the old promises. No longer do they insist that leaving will bring eternal sunshine. Now the best they can offer is the glum hope that things might, eventually, be no worse than if we stayed. Witness the pro-leave economist Andrew Lilico confidently telling the BBC earlier this summer that the country might recover from the transitional pain of Brexit by 2030.

When the best that can be said for leaving is that it might one day be as good as remaining, and when the worst points to national catastrophe, you might expect the public mood to shift. And yet the polls detect little sign of change. Overall, the two camps are broadly where they were on referendum day, with few leave voters having changed their mind.

The explanation surely lies in the nature of the 2016 vote. Remainers may wish it to have been based on a calm assessment of empirical evidence, so that fresh evidence now would shift opinions. But it wasn’t like that. Much of what drove that vote, like all votes, was emotion. This was remain’s weakness. And it still is.

Even now, anti-Brexiteers struggle to articulate a case that matches the emotional power of “take back control”. It certainly resonates when you say that it’s wrong to shrink the horizons of a generation of young Britons, who will now be denied easy access to an entire continent. But the deepest emotional argument for remain looked not to the future, but to the past. It centred on the second world war.

Facebook Twitter Pinterest ‘Donald Trump and the fascist contagion is reminding us why the EU exists: to ensure that the neighbourhood we live in is never again consumed by the flames of tyranny. Photograph: Alex Wong/Getty Images

It contemplated the long, lethal history of Europe and saw the European Union as the answer. For a continent that had been gripped by the fever of nationalism and hatred, the EU proved to be an antidote, soothing the brow with its spirit of co-operation and sharing of sovereignty. The Britain that had fought two world wars surely was obliged to cherish, rather than risk, this remedy to the European disease.

That argument barely flew in the referendum campaign. When David Cameron tried it, Boris Johnson mocked him for it. But mentioned even less was the conflict that followed 1945: the cold war that divided Europe with a wall and left the continent – and the world – in the permanent shadow of nuclear apocalypse. Its absence was strange, given that it had been Britain, and especially the British Conservative party, that after the cold war was over had seen the EU as the means to bind together a once-ruptured Europe. It was the Tories who pushed for EU enlargement, to include the ex-communist nations of the east. Once again, the EU’s mission was to heal a continent shattered by conflict.

A reminder of that vision has come this week not from a politician or pro-remain pamphleteer, but a fictional character. George Smiley, who lived the cold war in the shadows, returns in John le Carré’s masterful new novel, A Legacy of Spies. He makes a fleeting, enigmatic appearance in which he asks himself what was it all for. “I’m a European,” he says. “If I had an unattainable ideal, it was of leading Europe out of her darkness towards a new age of reason.”

Smiley, a veteran of both the hot war against fascism and the cold war against Soviet communism, had known that darkness first-hand. But for those who voted in last year’s EU referendum, perhaps it all seemed too long ago. Those demons were slain, the EU no longer needed.

Still, if that’s how it looked on 23 June 2016, it looks different now. In a talk on Thursday night, Le Carré spoke of the behaviour of Donald Trump and others as “absolutely comparable” to the rise of fascism in the 1930s. “It’s contagious, it’s infectious. Fascism is up and running in Poland and Hungary. There’s an encouragement about,” he said.

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This is a warning to take seriously. Hungary is indeed led by a man who boasts that he is building an “illiberal state”, while Poland’s government is trampling over fundamental democratic protections, including an independent judiciary and freedom of the press (and Trump is cheering them on as they do so).

The US president is not making America great again, but he is making the 1930s current again. Perhaps, then, and in a way he would not want, Trump is providing the anti-Brexiteers with the one thing they always lacked: an emotional heart to their argument. Trump and the fascist contagion is reminding us why the EU exists: to ensure that the neighbourhood we live in is never again consumed by the flames of tyranny and hatred.

On that fateful day in June 2016, it’s possible that some of those who voted leave did so because they believed that democracy and peace were now safe and secure in Europe. In the short time that has passed since, we have seen that those things are, in fact, fragile. As the head of Nato warns that the world is at its most dangerous point in a generation, Britain’s duty, to use a word that might make Smiley wince, is surely to defend the body that helped lead Europe out of its darkness. Instead, we are turning our backs and walking away.

• Jonathan Freedland is a Guardian columnist