The Obama people, not being idiots, understand very well that international terrorism possesses an overwhelmingly Muslim character. In Europe, where attention is so focused now, the great majority of the most lethal terrorist incidents of the past 15 years have been carried out by people professing to act from Islamist motives.Peter McKay, Canada's Justice Minister, recently illustrated the problem with this thinking, although he did so unintentionally. In his recent statement on the conspiracy to commit random mayhem in Halifax, Mr. McKay denied the conspiracy had any links to "terrorism". Since then, evidence has surfaced of a motive: the social media presence of at least some of the accused conspirators reveals a far-right wing orientation. Denying that a plot to commit random violence with no possible motive except for politics only makes sense in the context of a trope that effectively defines political violence as terrorism only if committed by Muslims.
Consider another example, the largest mass casualty act of political violence in the last twelve calendar months to take place in the geographic confines of Europe: the shooting down of Malaysia Airlines Flight 17 over the Eastern Ukraine. To the extent this attack involved any Muslims at all, it involved them as victims. It caused 298 deaths, by a long way the greatest number of deaths from an act of political violence last year, and for some time before. So why does neither David Frum nor the sources he quotes at least acknowledge this as a terrorist act? Because, by the definition in effective use by his contemporaries, it doesn't qualify. Muslims didn't do it.
Given the winds of political fashion, shorthand expressions that conceal absurd assumptions come and go all the time. These tropes only really matter when someone attempts to use them to establish a point of fact, and ends up seduced into stating something seriously out of line with the facts.