It was probably bound to happen — if not now, then eventually. There is an all-out war on the streets and almost inevitably somebody was going to be killed by the authorities who was believed to be implicated but then turned out not to be. Given the peculiarly ruthless tactic of suicide bombing, who could take the risk of allowing someone who seemed to be a plausible suspect to ignite himself in a public place? Given that we are up against an enemy who states categorically that he “loves death” as opposed to the weak and decadent West which so pathetically clings to life, how could anyone dare to assume that the likely man who chooses to run to the London Underground rather than stop on order is blameless? The Metropolitan police say this shooting of an apparently innocent man in Stockwell is a “tragedy”, as indeed it is. But what would the scale of the tragedy have been if they had given him the benefit of the doubt and got it wrong? How many nanoseconds do you have in which to make the choice? And what, as a law enforcement officer, is the inescapable priority? The Muslim extremists have produced something of a genuine martyr: a victim of what — if he proves to have been Muslim — may be described as the West’s Islamophobia, when he was a victim of the terrorist campaign itself. We must not equivocate about this. The outrage of the Muslim community will be genuine. The protests of the civil liberties lobby have so far been commendably muted, but the anti-war brigade, who will find yet more grounds for condemning our foreign policy, will be more vociferous than ever. But we are not to blame — that is, we as a society, we as a democracy, we as a population. We must not lose our grip on the truth: that Britain is a free, tolerant and generous country that has bent over backwards to accommodate its culturally diverse migrants.

The killing of this man is a small victory for Islamic terrorism which, like all movements that attempt to undermine societies from within, has always hoped to provoke the authorities into what could be described as persecution. (Old-fashioned communist agitation had a similar logic: cause the police to display the true “repressive nature of the capitalist state” and you will win converts.) It has thrown everything — including the lives of its own young — into the battle for the minds of the Muslim population who must be made to believe that their own country is the enemy. And it found the perfect strategy with which to do it. Not just mass murder, but self-destructive nihilism. How do you fight an enemy who is not only prepared to sacrifice his own life, but who positively wants to die? One who explicitly begs you for the opportunity to destroy himself? This is a small victory for a hatred that goes beyond politics, or nationalism, or tribal grievance, or any of the quasi-rational things that are subject to negotiation and reasonable argument. There is no debate to be had here. We are in the territory of outright madness. Those who pretend that there could be some accommodation with the aims of this movement — who see it as a new power balance in the world that must be addressed in foreign policy terms — are criminally irresponsible. There is nothing short of the extinction of democratic, secular society that would appease this enemy.

This new global confrontation is far more volatile than the cold war ever was. Back then, when we lived with our fears of a nuclear holocaust, we were up against a global debate about the quality of life. Capitalism and communism were both products of the 18th-century enlightenment. They were locked in a disagreement about how it was best to live: which system was most likely to produce the greatest happiness for the greatest number. Back then we were all humanists of a sort who believed that life was worth living and the way that societies were governed was critical to the welfare of our fellow men. The battle of ideas got messy and scary when everybody got the sort of weapons that could have put an end to life of all kinds. But the fact that the weapons were never used was no coincidence: in the end, they valued life too much on both sides of the divide.

Now we are at war with death itself and we cannot rely on that final rational decision to hold back from the brink. The man who ran on to the train at Stockwell station was caught in the hair’s-breadth of an inescapable moment: the moment that has no time for reflection or caution. Had he been what the police thought he was, any delay, any attempt at what we regard as reasonable doubt would have been a derogation of duty. Of course, the official independent inquiry that follows any such death will have to draw some clarity out of these hopelessly ambiguous circumstances.

Whether the enlightened voices within the Muslim community can persuade their brethren of this will be another thing. They will need enormous support and limitless effort from all of us. Their efforts will not be helped by the “we are all guilty” brigade who will turn this into yet another call for British self-loathing. There has been quite enough of that already.

We have had our absurd parade of bombastic, self-flagellating (and self-advertising) headline-grabbers who would happily play into the hands of those hoping to turn British Muslims into a community of malcontents. They have done their best to spread masochistic disillusion and defeatism. Now, please, let’s have an end to it. There had to be a turning point where the country’s anger and confusion would turn to resolve. If it is to mean anything, the resolution must involve self-belief and the confidence to persuade the majority of Muslims that their goodwill towards this adopted country is not misplaced.

The terrorists have provided the irreducible axiom for this confrontation: “We love death; you love life.” What happened at Stockwell Tube station was a hideous mistake but one that was made in the name of protecting life. There can be no moral equivalence between that killing and the deliberate murder of innocents that was the object of the successful terrorist attack of July 7 and the mercifully unsuccessful one of July 21. Life — and the preciousness of it — is what this is all about. Somehow, we have to hold on to that.

Minette Marrin is away