An important rule for building walls is to know when you are walling someone out and when you are walling yourself in. Friedrich Merz, the leader of Germany’s conservative CDU and likely next chancellor, is about to find this out the hard way. After two people — including a two-year-old child — were killed in a stabbing incident in the Bavarian town of Aschaffenburg and three more seriously injured, the German public is understandably angry.
