Michael Gove stood before the house with his elaborately courteous mien dialled up to the max. The secretary for levelling up is so polite now that it reads as a kind of schoolboy humility as he gallops through his words, mindful of the great honour of his colleagues’ attention. “The United Kingdom is a success story,” he said, “a multinational, multi-ethnic, multifaith democracy, stronger because of our diversity.” This was the preface to the government’s new extremism guidelines, and there’s a world in which a celebration of diversity would be a reassuring starting point. That’s not, unfortunately, the world we’re...