Violence is now, without doubt, a part of British politics, just as it is now, without doubt, a part of American politics. When I saw the first picture of Joshua Kerry, the man accused of murdering former British MP Ann Widdecombe, I knew without a moment’s hesitation. “This man is a leftist. The worst kind.” I said so on X, too. I’ve gotten in trouble before for suggesting there’s such a thing as “leftist physiognomy”—a distinctive set of physical features that instantly identify a person as a leftist, especially a radical one—but I’ll happily defend that position, no matter how...