‘Dark,” “divisive,” and “dangerous” were a few of the negative descriptors that critics attached to President Trump’s inaugural address, and those were just the ones that start with “d.” (A few threw in “dystopian” for good measure.) The critics took him this way in part because he depicted the last few decades of American life as a hellscape from which he would shortly deliver us: “This American carnage stops right here and stops right now.” But the critics also had this reaction because the address had a theme — nationalism — that has itself long been assumed in many quarters …