People always talk knowingly about Weimar, a period of extremes: artistic and social-sexual decadence, democratic liberalism and the radicalisation of the left and the right, before Germany’s descent into Hitlerian hell. The city as a symbol, close to the site of the former Buchenwald concentration camp, is back in the news, well, at least the op-ed pages of the Western press. That’s rarely a good sign. “The new crisis [in Germany] seems uncomfortably familiar because, in some respects, it...