Ian Buruma is professor of democracy, human rights and journalism at Bard College, and the author of Year Zero: A History of 1945.

There are many roads to political disaster: greed, hubris, the charisma of the demagogue and, perhaps most dangerous of all, fear. When people panic, they can become hysterical, and hysteria often leads to mass violence. When politicians convince people that they are in a life-or-death battle – that survival is a matter of "us or them" – anything becomes possible.

Adolf Hitler combined all the elements of political catastrophe: hubris, charisma, greed and the idea that "Aryans" and Jews were locked in a struggle for survival. Of course, none of the demagogues in the West today – from Donald Trump in the United States to Marine Le Pen or Geert Wilders in Europe – are comparable to Hitler. None has promoted dictatorship, let alone mass murder. But they are definitely stirring up the politics of fear.

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Mr. Trump, for one, also promotes greed, openly boasting of his wealth, and has somehow refined outlandish hubris and contradictory posturing into a bizarre form of charisma. On the one hand, he promises to fix all the world's problems, and to show China, Russia, the Islamic State, or anyone else, who is boss. On the other hand, he claims that his vast and powerful country cannot take in desperate refugees from Syria, because, he warns, Muslim asylum-seekers might stage "one of the great military coups of all time."

Mr. Trump's Republican colleagues in the race for the U.S. presidency, such as Ted Cruz, Ben Carson and Marco Rubio, stoke similar fears about refugees. Mr. Cruz, as well as the supposedly more moderate Jeb Bush, even suggested that only Christians should be allowed into the United States.

More than 10,000 people are killed every year by gun violence in the U.S. – all but a handful for reasons having nothing to do with Islam. And yet all of the Republican candidates are proud of opposing gun-control measures; indeed, they have no problem allowing people to enter a school or a bar bearing concealed weapons. But even a relative handful of Muslim refugees is too dangerous to contemplate.

This is not to say that terrible acts of Islamist terror could not happen in the U.S., or elsewhere. They have, and there probably will be more of them, so long as the Middle East remains in turmoil and revolutionary Islam appeals to disaffected Western youth. But it is hardly an existential threat.

The greater danger is, however, that the demagogues will drive even mainstream politicians into their camp. Since the Nov. 13 terror attacks in Paris, François Hollande, the unpopular but altogether sensible French president, has been so afraid of being labelled a weakling by politicians of the right and far right that he has declared a national state of emergency – and war on the Islamic State.

As long as France's state of emergency lasts, police may arrest people without warrants, break down the doors of private residences in the middle of the night, take over restaurants and other public places with armed force, and generally behave like agents in a police state. Most French citizens are now so frightened of Islamist attacks that such measures are widely supported. But they are almost certainly counterproductive.

A national leader can declare war on a state, not on a network of revolutionaries. Islamic State, despite its claims, is not a state, and Mr. Hollande should not treat it as one. Besides, even if bombing IS strongholds in Iraq or Syria makes military sense, it won't break the spell of Islamist revolution for frustrated, bored and marginalized young people in French slums.

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On the contrary: The canny leaders of IS also rely on an apocalyptic "us or them" view of the world. Most Muslims are not violent revolutionaries who condone, let alone admire, mass violence. IS seeks to broaden its support, especially among young Muslims, by convincing them that true Muslims are in an existential war with the West – that the infidels are their mortal enemies. For them no less than for Mr. Trump, fear is the most powerful weapon.

So the more a Western government allows its policemen to humiliate and bully Muslims in the name of security, the more IS is likely to win European recruits. The only way to combat revolutionary Islamist violence is to gain the trust of law-abiding Muslims in the West. This will not be easy, but arbitrary arrests are surely the wrong way to go about it.

Likewise, when it comes to civil wars in the Middle East, Western restraint is usually a better strategy than hasty military intervention driven by domestic fear. Republican candidates in the United States are already using the recent murder spree in Paris to blame President Barack Obama, and by extension any future Democratic candidate, for being weak. Mr. Trump has promised to "bomb the shit out of ISIS."

This bellicosity has had the effect of pushing Hillary Clinton, the front-runner for the Democratic presidential nomination, into distancing herself from Mr. Obama. As with Mr. Hollande, she has to assuage public fear by talking tough and promising more military action.

Mr. Obama has consistently resisted the temptation to unleash more wars. His policies have sometimes been inconsistent and irresolute. But in his refusal to give in to panic and act rashly, he has been far braver than all the big talkers who accuse him of being a wimp.

Copyright: Project Syndicate, 2015.