Editor's note: This post is part of a series by Dr. Baker on Our Values about core American values. This week Dr. Baker is discussing Syria.

The Syrian regime has killed thousands of its own citizens, using conventional methods of war. Over a million people have been displaced. But the alleged use of Sarin gas crossed a bright red line, inviting military attacks by the United States and other nations.

The values question for today is: Why does it seem to be okay to kill with bullets and bombs—but not okay to kill with chemical weapons? Obviously, all killing is tragic, especially when it involves unarmed civilians. But the international community has identified the use of chemical weapons as a moral red line.

Dominic Tierney, writing in The Atlantic, puts it this way: “Oddly, the international community seems less concerned by how many people the Syrian regime kills than by the methods it uses to kill them.” He argues that the reason might be strategic. Superpowers like the U.S. can win wars that use conventional weapons, but weapons of mass destruction (like poison gas) “have a vast advantage in conventional arms,” leveling the playing field.

Others cite the cruelty of death by chemical means, akin to the horrible deaths in World War I by the use of mustard gas. But, says Paul Waldman in The American Prospect, “Getting killed by mustard gas is surely awful. But so is getting blown up by a bomb. Using one against your enemies gets you branded a war criminal, but using the other doesn’t.”

What is it about chemical weapons that especially terrify us—or seem especially wrong?

Does the use of chemical weapons cross a red line for you?

Or, does the murder of citizens by any means cross the red line?

Wayne Baker is a sociologist on the faculty of the University of Michigan Ross School of Business. Baker blogs daily at Our Values and can be reached at ourvaluesproject@gmail.com or on Facebook.