A few weeks ago, when it still looked as if the US might fly air strikes against Syrian government facilities, Stratfor had one of their typical insightful analyses.
As part of this they point out the cognitive dissonance characterizing the stance of the US government with regard to weapons of mass destruction (WMDs):
One was U.S. concerns over weapons of mass destruction. From the beginning of the Cold War until the present, the fear of nuclear weapons has haunted the American psyche. Some would say that this is odd given that the United States is the only nation that has used atomic bombs. I would argue that it is precisely because of this. Between Hiroshima and mutual assured destruction there was a reasonable dread of the consequences of nuclear war. Pearl Harbor had created the fear that war might come unexpectedly at any moment, and intimate awareness of Hiroshima and Nagasaki generated fear of sudden annihilation in the United States.
Other weapons capable of massive annihilation of populations joined nuclear weapons, primarily biological and chemical weapons. Robert Oppenheimer, who oversaw the scientific work of the Manhattan Project, employed the term “weapon of mass destruction” to denote a class of weapons able to cause destruction on the scale of Hiroshima and beyond, a category that could include biological and chemical weapons.
The concept of weapons of mass destruction eventually shifted from “mass destruction” to the weapon itself. The use and even possession of such weapons by actors who previously had not possessed them came to be seen as a threat to the United States. The threshold of mass destruction ceased to be the significant measure, and instead the cause of death in a given attack took center stage. Tens of thousands have died in the Syrian civil war. The only difference in the deaths that prompted Obama’s threats was that chemical weapons had caused them. That distinction alone caused the U.S. foreign policy apparatus to change its strategy. (my emphasis)