The bearded Oracle of Islington proffered two lessons to the nation yesterday.

First, he explained to the people of Northern Ireland that there was “almost some kind of equivalency” between the IRA and the British Army – displaying a jaw-dropping refusal to condemn bombers and gunmen who slaughtered thousands of people, mostly civilians. Some of the listeners of BBC Radio Ulster could be forgiven for thinking that position is rather easier to hold as an MP who sucked up to the terrorists in the safety of the Commons tearoom than as one of the defenceless families who spent decades living with the ever-present threat of beatings, torture and murder.

He wasn’t done, though – that was just the morning shift. Later on, he told a CND gathering that engineers working on Trident would be reallocated to “socially useful” work. This says it all, really – for the hard left, defending Britain is not “socially useful” – either because they don’t think Britain is worth defending, or they think that defence is a deeply unpleasant thing to do, pursued by dreadfully rough people who simply can’t manage a civilised conversation with our “friends” in Hamas, Hezbollah and elsewhere. Needless to say, Russia Today, Vladimir Putin’s pet television channel, spent yesterday nodding in agreement.

It is easy to laugh at Jeremy Corbyn and his fellow travellers. This site has done so before, and I dare say it will do so again. But we must also remember that beneath their absurdity lies danger. It always has – from the days of the happy clappy CND protesters who seemed so convinced that the evil dictators of the Soviet Union would generously decommission their own missiles if only we dropped our guard, to the age of a surging Labour leadership candidate who merrily takes tea with bombers but thinks loyal Trident engineers are socially useless.

Voters naturally dislike and distrust such views, but that doesn’t mean we should be complacent. In a few short months this lunacy has gone from the very far fringes of the Labour Party to gaining the support of a large chunk of its membership – while we mock it, let’s retain a firm determination to defeat it at every turn.