In the Vladimir Putin showreel, doubtless given repeat airings in the run-up to Sunday’s presidential faux election, there’s usually a place among the shirtless poses and horseback shots for images of the Russian leader on the judo mat. Putin is such a committed judoka, he has even put out his own instructional DVD, wittily titled: Let’s Learn Judo with Vladimir Putin.

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It is not hard to explain Putin’s enthusiasm for the martial art, beyond its conspicuous machismo. For judo allows the skilled practitioner to turn his opponent’s strengths into weaknesses, and his own weaknesses into strengths. For the past fortnight, since the attempted murder of Sergei and Yulia Skripal on the streets of Salisbury, Putin has been giving a masterclass in how it’s done.

He has shown us how he sees, for example, the basic tenets of democracy – whether that’s free speech or belief in the rule of law, evidence and due process. To us, those may look like the firm pillars that hold up a decent society. But to a black-belt such as Putin they are rotten timbers, ripe for a good kicking and liable to bring down the whole edifice.

Take the political response to the Salisbury attack. On the face of it, Jeremy Corbyn’s position, as set out in the Guardian yesterday, seems eminently reasonable. Anxious to learn the lessons of the Iraq catastrophe of 2003, he suggested we exercise patience: let’s wait and see where the investigation leads, let’s not “rush way ahead of the evidence”. After all, said his spokesman, the intelligence agencies had been wrong before.

Such a stance seems not just authentic for Corbyn, given his long record, but also right. Who could possibly be against such a call for calm and deliberation?

Put aside the fact that Corbyn’s position is oddly contradictory. If Moscow’s guilt is not certain, why does he support Theresa May’s expulsion of 23 Russian diplomats? By his own logic, surely that move too should wait until the case is proven. Put aside too the mismatch between this incident and the Iraq case. No one is calling for military action now. Back then, the argument was over whether to deal pre-emptively with a threat of weapons of mass destruction that might or might not exist, in a country several thousand miles away. This time, the question is how to respond to an event that has actually happened and which no one denies: the use of a chemical weapon against civilians on a British street.

What’s more, there is Russia’s past form. The roll-call of murdered enemies of the Russian state is long. We know Moscow is not above eliminating its critics in Britain: witness the 2006 death of Alexander Litvinenko and the murder inquiry Scotland Yard announced late on Friday into the death of the Russian businessman Nikolai Glushkov.

As for the suggestion that a criminal gang, rather than agents of the Kremlin, may be responsible, the experts are sceptical: it’s near-impossible to use novichok without getting killed unless you know what you’re doing. It’s for these reasons, among others, that Britain, Germany, France and the US issued a joint statement concluding that there was “no plausible alternative explanation” for the attack in Salisbury.

But those pleas to delay judgment point to a wider error: a misreading of the nature of the contemporary Russian state. In fairness to Corbyn, he is not the only one to make this mistake. Donald Trump’s initial reaction was also to plead for patience and to suggest that guilt may lie elsewhere. As he memorably put it, “As soon as we get the facts straight, if we agree with them, we will condemn Russia or whoever it may be.”

The error here is to assume that Moscow’s attitude to evidence and due process is the same as that of nations still governed by the rule of law. But in Putin’s Russia, lying has long been a routine and integral part of statecraft. No matter how copious the evidence, Putin will think nothing of denying it. In 2014, he swore there were no Russian troops in Crimea, even though reporters could see them with their own eyes. “Anyone could buy” Russian uniforms, he said. Weeks later he was paying tribute to those Russian troops, with nary a blush.

Labour should be calling for an EU-wide visa blacklist of Kremlin officials

That same year Moscow waved aside evidence relating to the downing of Malaysian Airlines flight MH17 over Ukraine. It continues to block investigations into the use of chemical weapons by its Syrian vassal, Bashar al-Assad. Putin denies hacking the 2016 US presidential elections, in the face of colossal evidence. And of course he denied any role in the murder of Litvinenko, though he did later ensure the killer got a seat in the Russian parliament, thereby granting him immunity from prosecution.

What meaning does “due process” have when dealing with such a regime? Moscow would not cooperate in good faith with an investigation by the international chemical weapons watchdog, offering up evidence that might be incriminating. They would see such an inquiry instead as a useful delaying tactic, one that would allow them to issue yet more denials, wild counter-accusations (“Salisbury was an MI5 plot to distract from Brexit”) and obfuscation – disseminated either through their RT propaganda TV station or by their army of bots and online enablers. That way they could generate yet more of the fog of doubt and confusion that they believe undermines the west’s confidence and strengthens them. This is the Putin modus operandi: spread doubt until the public grows exhausted and concludes that the truth is unknowable.

So we need to be clear-eyed about the nature of the threat. We should not overstate it: Russia’s economy is no bigger than the combined output of the Netherlands and Belgium. But nor should we underestimate it. Corbyn condemned the Putin regime for its “conservative authoritarianism”. That doesn’t quite cut it. Norman Tebbit is a conservative authoritarian. Vladimir Putin is a murderous tyrant, who kills or jails his rivals and has the blood of hundreds of thousands of Syrians, Chechens and others on his hands.

Labour should be calling for an EU-wide visa blacklist of Kremlin officials, restricting their ability to enjoy Europe’s playgrounds; for a crackdown on the City banks and law firms that allow Putin’s allies’ money to be laundered through London; and, as MP Margaret Hodge urges today, for May’s proposed transparent property register to be brought forward from 2021 to right now.

But above all, Labour and the rest of us need to see Putin for what he is. Not an admirable bulwark against US imperialism, but an ultra-nationalist bent on fomenting hate and division; an idol to Nigel Farage, Marine Le Pen and Trump who sees our democratic and legal traditions as weaknesses to be exploited. We must give him that chance no longer.

• Jonathan Freedland is a Guardian columnist