The ongoing argument about Jeremy Corbyn's consistent support for the "armed struggle" of the Provisional IRA is vacuous and circular. Very few people endorse every single action of any group they support, but Corbyn and his circle were always there to lend their support, particularly when the Provisionals were in difficulty.
There are thousands of Labour supporters, in both islands, who were involved in this area over many years and who know that Corbyn and a small group of extreme Leftists in Britain made common cause with the most extreme violent nationalists in Ireland in order to advance what they saw as revolutionary struggle.
From the Socialist Workers Party to the two foot soldiers of Red Action who were convicted of the 1993 Harrods bomb, a bewildering array of fanatics found common cause where Ireland was concerned. They largely took their inspiration from James Connolly, the Edinburgh-born Marxist of Irish parentage who was executed in Dublin after the 1916 Easter Rising.
His writings, widely read in those circles, and the fact that he fought and died alongside extreme Irish nationalists, formed the rather threadbare intellectual background. At least Connolly had the decency to fight and die in Ireland. This bunch were polishing their revolutionary credentials with the blood of the British and Irish working class.
Industrialists who brought jobs to Northern Ireland were murdered. Factories were blown up and working people put out of employment. Trade unionists, some members of unions affiliated to the British Labour Party, were murdered. Just last week I gave evidence to an inquest in Belfast concerning the murder of 10 Protestants returning from their day's work who were taken out and slaughtered on the side of the road by the Provisional IRA.
When I watch or hear Corbyn deny his lifelong support for the Provisional IRA I know with absolute certainty that there are many members, senior and otherwise, of the British Labour movement who feel the same revulsion as I and many others in Ireland do.
Many good and decent people within the Labour movement - former Secretaries of State for Northern Ireland, former Prime Ministers, MPs, union leaders, labour and trade union activists - fought tooth and nail against both the IRA and its apologists.
Who within the British Labour movement will speak out and demolish the lie that is being repeated every day right now by Corbyn, John McDonnell and Diane Abbott that they did not support the IRA? They can only repeat it while the people who fought them within the Labour movement for years remain silent.
Those who do so have become, in effect, facilitators of the most monstrous lie peddled in British politics in living memory. This is on an utterly different plane from the ordinary cut and thrust of politics, or the pursuit of electoral victory. Those who know the truth and remain silent must and should be ashamed of themselves.
Some of these people are good friends of mine, others I have admired greatly. We stood up and made common cause against a small bunch of zealots who would have brought the peace process crashing down.
It doesn't matter that the events were 10, 20 or 30 years ago. We must stand up again: those zealots are now repeating a lie, a murderous lie, every day as they try and rewrite history in a grotesque and squalid pursuit of power.
A lie of this nature, if allowed to go unchallenged within the Labour movement, will eat into its very soul. That is not some arcane philosophical claptrap. It is a brutal tyranny of fact.
Go with this lie and you set a match to your conscience. It is time now for all those honourable people in the Labour movement, who have authority and know the truth, to do the right thing. If you need further convincing, think of a Northern Ireland ruled by Prime Minister Corbyn, McDonnell and Abbott.
Picture the rapture on the face of Sinn Fein's Gerry Adams and his comrades as their lifelong supporters ride in to take charge. Think of all that and much more, and shudder at the prospect that lies ahead for both islands.
Sean O'Callaghan is the author of James Connolly: My Search For The Man, The Myth And His Legacy (Penguin/Random House, 2016). This article first appeared in The Spectator (www.spectator.co.uk)