At today’s debate in Parliament on ‘Approval of Military Action’, Jeremy Corbyn brandished a copy of the Chilcot Inquiry at Theresa May and called it “a salutary lesson to all of us”.

There are lots of things about Corbyn that are utterly disgraceful: his wilful blindness on anti-Semitism; his wilful blindness to the crimes of twentieth century socialism; his wilful blindness on the failures of Chavez in Venezuela; and his wilful blindness on Russia’s violations of international norms.

But there is nothing there that is quite as galling as his facile opposition to all forms of Western intervention in all conflict zones. For him, the Iraq experience dominates. He can’t see past it. I can understand why – Corbyn has spent his whole career without decoration for public service and without ministerial appointment. The Iraq experience was a definite high point. It must have been an exciting time for his coterie of fanatics – an imperialist war to oppose, marches to organise, speeches to make.

There were of course plenty of reasons to oppose the intervention in Iraq on principle. It was an exception to the interventions staged by UN authorities in the nineties. Genocide had been used by the Saddam regime against the Kurds in 1991, but that’s not why the intervention was launched. It was launched in an atmosphere of hysteria and anxiety post 9/11.

It is quite possible to defend liberal interventionism, which is a complex and multi-faceted thing. In the nineties, the West, in concert with the UN, did extraordinary things. Interventionism was mostly worth defending. We launched military interventions on a large scale in East Timor and Kosovo but that was only part of it. Those interventions were followed by well-resourced state building exercises. We also launched inquiries into extrajudicial killing, transitional justice mechanisms in South America and in Africa, and Truth and Reconciliation commissions across the world.

Corbyn’s response to intervention in Kosovo was particularly unforgivable. He signed an Early Day Motion brought to parliament in 2004 that alleged that the intervention in Kosovo had been launched with “fraudulent justifications for … a ‘genocide’ that never really existed in Kosovo”. His spin doctor Seumas Milne wrote in 2001 that “the new Belgrade administration dug up corpses to order” in order to provide a basis for the prosecution of Slobodan Milosevic at the Hague.

Corbyn is no man of principle. His explicit sympathy for those who sought to deny a genocide in Bosnia shows in obvious terms that Corbyn has no principled critique of interventionism. His is a critique grounded in hatred of the West, and in sympathy for those who violate international norms in the name of anti-Western opposition.

We have known for years that war crimes were being committed in Syria by the state apparatus. We should have launched a vast, large-scale intervention in 2012. We should not have let Russia define the conflict on its own terms.

We should have empowered the liberal opposition – for there were many thousands of people who marched for freedom in the Arab Spring. There were massive, massive rallies, dancing, and a sense of joy: joy at the prospect of new freedoms that would seem quite unremarkable to us in the West – a civil state, freedom of expression, and free and fair elections.

What happened to them? They were systematically destroyed. The Syrian government, with its formidable bureaucracy, wiped them out by means of torture, execution and mass extermination.

Corbyn always asks for ‘incontrovertible evidence’. There is. A Channel 4 documentary aired last year, ‘Syria’s Disappeared: The Case against Assad’, shows with clarity that there is a legal basis for a prosecution of the Assad regime for Crimes against Humanity. A whistle-blower, code named Caesar, defected to the West, bringing thousands of photos and documentary evidence. I repeat – Syria is a formidable bureaucracy. Everything is accounted for by document; everything is signed off. The documentary evidence leads straight to the Presidential palace: the command chain is clear and well-defined.

There are 6,700 corpses in those files alone. Remember these names: Tishreen Military Hospital, Hospital 601, and Mezze Airforce Intelligence facility. It was there that most of the killings took place.

We have known all this for years. We had the power to act in 2013 but we chose not to. We had the resources and the firepower. We are all Assad’s useful idiots now.