Celebrating the 50th anniversary of the March on Washington last week, President Obama said the event demonstrated “the moral force of nonviolence,” as indeed it did.

But it did so in a country that extols and practices nonviolence, a principle whose moral force goes unrecognized in most of the non-Western world, particularly the Middle East.

Recent events in Syria — namely, the government’s use of chemical weapons last month to kill hundreds of civilians — make this all too clear.

As one would expect, most of the non-Syrian world condemned the Assad regime’s actions. Secretary of State John Kerry called the use of chemical weapons “a cowardly crime.”

British Prime Minister David Cameron said it was “morally indefensible.” White House Press Secretary Jay Carney, sounding a different note, called it “a specific violation of international norms.” All are accurate.

What are we to do? Something, apparently. After all, a year ago Obama said that “a red line” would be crossed in Syria if “we start seeing a whole bunch of chemical weapons moving around or being utilized.”

“President Obama,” Kerry said last week, “believes there must be accountability for those who would use the world’s most heinous weapons against the world’s most vulnerable people.”

As a matter of policy, that is all well and good so far as it goes — which is not very far — but, as a moral statement, it is sorely incomprehensive. After all, how often are the world’s most heinous weapons used? Not very often.

And so, one wonders, does the president also believe in accountability for those who employ less heinous but equally deadly weapons — say, rifles — against less vulnerable people — say, Canadians? Let us remember that rifles also can be weapons of mass destruction, provided enough of them are fired. But heinous they are not.

For civilized nations, the question of accountability arises only when our vital interests are at stake or when our collective conscience is sufficiently “shocked.”

“What we saw in Syria last [month] should shock the conscience of the world,” Kerry said. “It defies any code of morality. Let me be clear: The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons, is a moral obscenity.”

Is one to infer from these comments that the slaughter of civilians by non-chemical weapons is somehow less obscene or less shocking? Well, yes. Nonchemical warfare is, visually at least, arguably less obscene and certainly less shocking.

This is for a simple reason: We are more accustomed to guns than to poison gas. Policemen and law-abiding citizens use the former, madmen the latter — and even then, rarely.

We can make distinctions between various methods of murder when those distinctions are made for us. It is harder to relate to victims of firing squads, for instance, than to people who breathe. We all breathe, and none of us wants to die because of it. In Syria, the Assad regime has made respiration a crime, punishable by asphyxiation.

What is the proper response to a government that deliberately suffocates its own citizens? Moral indignation is the easy route, available to hawks and doves alike, and also the most frequently chosen. But to the extent that moral arguments have any sway, it is only in societies that abstain from violence, of which Syria is not one.

In 1941, George Orwell reviewed a novel by an English pacifist in which the protagonist decides that instead of fighting the Nazis, he will “overcome Hitler by love.” Not coincidentally, this was a work of fiction.

“Those who ‘abjure’ violence,” Orwell wrote four years later, “can only do so because others are committing violence on their behalf.” Nonviolence is a luxury, in other words, and one we too often take for granted.

The sad reality is that, in much of the world, morality backed by nonviolence is futile against immorality backed by violence. Poison cannot be overcome by love. That is why there will be no march on Damascus.

Windsor Mann is the editor of The Quotable Hitchens: From Alcohol to Zio.