The far left’s argument in favour of Brexit is a mess of invented histories, smears, crocodile tears and paranoia. Worse, it’s a party line that is repeated by propagandists out of deference to the leadership. If the leadership should stand on its head and announce it supported Britain staying in the EU or remaining a member of the single market, Corbyn's supporters would stand on their heads too. The radicals who are now chanting “where’s Jeremy Corbyn?” may not study the intricacies of Labour Party politics – why should they waste their time when we are facing a national crisis? – but they cannot miss the overpowering odour of insincerity.

Labour’s bad faith is built on two dishonesties. Jeremy Corbyn and John McDonnell have opposed the EU throughout their political careers. Their stance sets them at odds with most of Europe’s Marxist and post-Marxist parties. Podemos in Spain, Syriza in Greece and Jean-Luc Melenchon in France are highly critical of the EU for good reasons, but they don’t want to leave it. In an era when capital is international, they reason, the institutions that might restrain it must be international too.

The Bennites the young Corbyn joined, and what we used to call the “tankie” faction in the British Communist party, never accepted the need for internationalism. A cynic could say that the old left was following the lead of the Soviet Union, which no more wanted a strong Europe in the 1970s than Putin does today. Too harsh? I don’t know. As I’ve said before, the difficulty with writing about the left's case for Brexit is that Corbyn and McDonnell never argue it in public. Labour has become another hierarchical British institution where subordinates are expected to know what the party line is without being told.

Instead of explaining himself honestly, Corbyn descends into Johnsonian cakery and promises a ‘jobs first’ Brexit. The only possible way of limiting the damage to jobs from Brexit is for Britain to remain in the single market. Despite the efforts of Keir Starmer to move the party towards a coherent anti-Conservative position, Labour won’t commit to that because single market membership will allow freedom of movement to continue (a freedom that moves in both directions, as the forgotten Brits living in the EU would emphasise, if the Brexiteers wanted to listen).

For anyone with a sense of history, there are multiple ironies to savour. Labour was founded to represent the industrial working class. Leaving the single market will wreck manufacturing, as Airbus and the car industry are warning. Yet Labour, the party of workers by hand and brain, will not fight. Nor, more egregiously, will it argue. The car workers in Sunderland may have voted to leave in protest against EU immigration. An honest Labour leadership, a leadership that still had connections to its party’s roots, would confront them with the consequences and try to negotiate a compromise. Britain, it would say, can end freedom of movement; but the price may well be your job. Instead, a left that once denounced real and imagined racists prefers to ally with the Labour right, and with May, Johnson, Farage and Banks. It has prioritised immigration controls above all else, and decided that stopping the arrival of foreigners from the continent is a hill fit for a left wing party to die on.

Corbyn supporting journalists are responding to the feeling that radical politics is moving away from them with what students of communist history would call the tactics of “third period” Marxism-Leninism. (And who would have guessed we would have to dig up that old junk in the 21st century?) Just as in the late 1920s and early 1930s when the Kremlin ordered the world’s communists to turn on social democrats rather than the fascists who were preparing for power in Germany, so today Corbyn’s propagandists fight leftists who want to fight Boris Johnson and Nigel Farage rather than, for instance, Boris Johnson and Nigel Farage.

Aaron Bastani goes on television to accuse a young activist of being a Tory stooge because she may have worked in the same office block as a former Conservative minister.

“Causing a public nuisance I suppose so, why not” @AaronBastani on Our Future Our Choice asked to leave #LabourLive after unveiling Stop Backing Brexit banner in #bbcdp debate with @tessmillsy pic.twitter.com/OftIdWW8ZQ

— BBC Daily Politics and Sunday Politics (@daily_politics) June 21, 2018

He rules that no one can build alliances against Brexit because anti-government coalitions mean sharing 'a platform with Tory and Lib Dems behind austerity and Alastair Campbell’ (a Blairite, I should explain, and thus a carrier of another contagious disease that brings political death to all who encounter it).

In the ‘more in sorrow than anger’ tone of a school master explaining why a punishment hurts him as much as it hurts you, Owen Jones tells leftists they cannot demand a second referendum. He shares their pain, really he does, and would love to stay in the EU. But asking the country to think again would 'boost the radical right'.

I have a little sympathy for his argument. I would have considerably more if Corbynites showed the slightest understanding that the right has to present the inevitable failure of Brexit as a Weimaresque stab in the back regardless of whether there is a second referendum or not. Indeed it already is. Hence the talk of the EU punishing Britain, and judges and independent-minded Tory MPs betraying 'the people'.

But understanding requires an open mind willing to engage in robust political argument. And there’s the rub. Corbyn's supporters cannot speak plainly or argue honestly. Like so many far left movements in the past, they have trapped themselves in a personality cult. 'Jeremy' supports Brexit, and until he changes his mind, they must support it too. There's nothing more to say.

I don’t believe the conformists can hold the line. Momentum members set up a pro-EU campaign this week, while all the time repeating their loyalty to 'Jeremy'. As Labour members oppose Brexit overwhelmingly, their work would be unremarkable were it not that dissent is a kind of treason on today's left. Courage isn't an abstract quality. It depends on who you are and where you stand. Although it is easy to mock their timidity, their nervous attempt to assert their political independence is a taste of what is to come.

Radical politics is moving fast. In the spirit of fraternal goodwill, and with the well-being of my comrades at the forefront of my mind, I say to the Corbynistas that they also need to move if they do not want to end as despised and irrelevant as the Blairites they are increasingly resembling.