It has been a grim couple of weeks in the US, as multiple acts of politically motivated violence have dominated headlines and sparked fears that a worrying new normal has taken hold in America. Last Saturday, a man disguised as a police officer attacked two Democratic legislators at their homes in Minnesota, killing a state representative and her husband, and wounding another lawmaker and his wife. The alleged murderer was planning further attacks, police said, on local politicians and abortion rights advocates. The same day, during national “No Kings” demonstrations against the Trump administration, there was a spate of other...