Somehow, the accent makes all the difference. The murderer in the Islamic State videos speaks “Jafaican,” a street cant that young people from different ethnic backgrounds across southern England have picked up. I’m not sure what the closest American equivalent would be: Perhaps the painful way in which some white boys try to talk like rappers. In any event, Jihadi John’s dialect serves to emphasize the emptiness and vanity of his message. When we see hooded Islamists talking in musical, aspirated Arabic, we assume that something is being lost in translation. But self-regarding diatribes in this debased patois irresistibly recall Hannah Arendt’s phrase, “the banality of evil”.

What attracts boys from comfortable Western homes to such evil? Is it something in their religion, something in their socio-economic circumstances or something in their character?

There are several factors at work, and we should be wary of oversimplifying, but one observation made by almost all the experts who study Western-born militants is that they fit the profile of the terrorist down the ages: male, typically in their twenties, with some education, narcissistic, lacking in empathy, lonely, unsuccessful with women, often with a history of petty crime.

What turns such a young man into a terrorist? Finding a cause that validates his anti-social tendencies — a doctrine that teaches him that he is angry not because there’s something wrong with him, but because there’s something wrong with everyone else. Islamic State thugs, like (say) Baader-Meinhof gangsters, are convinced that they can see things more keenly than others, and that this clarity of vision ennobles their aggression.

Sure enough, the man identified by media as likely to be Jihadi John, far from being devout, is a rapper with a history of drug abuse. OK, we can’t be certain of his identity, but he would hardly be unusual. Consider, for example, Michael Adebolajo, who carried out the sickening murder of an off-duty British soldier in Woolwich, in southeast London. His was a textbook terrorist personality: a history of juvenile crime, substance abuse and anti-social behavior, an obsession with violent video games, a streak of raw belligerence (neighbors recall that he once punched a girl in the face when she came to retrieve a ball). Whatever else we call such a lifestyle, it’s hardly pious.

This point seems counter-intuitive, but it’s vital to an understanding of what we’re dealing with. Most of these boys seem to be attracted not by religion, but by glamour — the image of themselves as soldiers in a higher cause.

Indeed, Western jihadis are often astonishingly ignorant of the faith they claim to hold. Two young Muslims from Birmingham intercepted on their way to Syria were found to have ordered books from Amazon before they left. Not works on politics or warfare or advanced theology, but Islam for Dummies and The Koran for Dummies. Dummies indeed.

The great historian Lord Macaulay said something very true back in the 1840s: “The experience of many ages proves that men may be ready to fight to the death, and to persecute without pity, for a religion whose creed they do not understand, and whose precepts they habitually disobey.”

Quite. A leaked report from MI5 revealed that Western fighters in Iraq and Syria makes the same point in duller prose: “Far from being religious zealots, a large number of those involved in terrorism do not practice their faith regularly.”

That’s not to say, obviously, that there is no link with religion. Western jihadis may be drawn by what one security expert calls “a thrilling cause and call to action that promises glory and esteem in the eyes of friends,” but such enthusiasm is rarer in non-Muslim communities: You won’t find many Episcopalians, say, going out to fight for their coreligionists in Nigeria. Still, it’s critically important to understand the precise nature of the link.

It’s often argued that moderate Muslims should speak out more loudly against the terrorists. But this is already happening: The Islamic State is condemned in mosques around the world. British imams were quick to pronounce a fatwah against it. The trouble is that moderate Muslims are virtually the last people the extremists will listen to. Like most terrorists, the jihadis are attracted precisely by the unattainable purity of their creed. The kind of Wahhabism they favor makes no concession, either to existing practice or to human frailty. They regard mainstream Muslims as traitors.

If neither theological refutation nor the disapprobation of their community is effective, what can we do? Well, for a start, we can stop taking these losers at their own estimation. Treat them not as soldiers, but as common criminals. Instead of making documentaries about powerful, shadowy terrorist networks, laugh at the pitiable jerks who end up in our courts. Mock their underpants bombs and their shoe bombs and their tendency to blow themselves up in error. Scour away any sense that they represent a threat to the state — the illicit thrill of which is what attracts alienated young men trawling the web from their mother’s basements.

At the same time, let’s stop teaching the children of Muslim immigrants to despise the West. Let’s stop deriding and traducing our values. Let’s stop presenting our history as a hateful chronicle of racism and exploitation. The best way to defeat a bad idea is with a better one. Few ideas are as wretched as the theocracy favored by Islamic State; none is as attractive as freedom. We shouldn’t be shy of saying so.

In the end, this struggle comes down to self-belief. Not theirs; ours.

Dan Hannan is a British Conservative MEP