If a 22-year-old Muslim man stabbed his roommates to death in their sleep, embarked on a killing spree, and claimed in written and video manifestos that he acted to teach hated women a lesson, there's little doubt that many would label him a terrorist. That label was scarcely appended to the Santa Barbara killer after his murders.

And if a Muslim couple stormed into a fast-food restaurant armed with a duffel bag full of military gear, shouted, "This is the beginning of the revolution!" and pinned a flag associated with their political movement to the dead bodies of the police officers they executed at point-blank range—then killed another innocent person and carried out a suicide pact rather than being taken alive—there is no doubt that many media outlets would refer to the premeditated attack as an act of terrorism. With a few exceptions, that's not how this week's news from Las Vegas played out.

When mass killers are native-born whites, their motivations are treated like a mystery to unraveled rather than a foregone conclusion. And that is as it ought to be. Hesitating to dub the Santa Barbara and Las Vegas murder sprees "terrorist attacks" is likely the right call. The label casts more heat than light on breaking-news events. Americans typically respond more soberly and rationally to mass killings than to "terrorist attacks." And while both sprees obviously targeted civilians, the varying degrees to which they sought to influence politics is unclear.

That said, the pervasive double-standard that prevails is nevertheless objectionable. As Glenn Greenwald once observed, "terrorism" is "simultaneously the single most meaningless and most manipulated word in the American political lexicon. The term now has virtually nothing to do with the act itself and everything to do with the identity of the actor, especially his or her religious identity."