This summer, our reporting on Facebook’s links to real-world violence led us to Hagen, a quiet town in Germany’s liberal but post-industrial northwest, for a meeting with Gerhard Pauli, a local prosecutor.
At one point in the interview, Mr. Pauli, who is warm, grandfatherly and bears more than a passing resemblance to Matlock, retrieved a heavy binder from storage. It contained hundred of pages, each with a message or meme that the police had pulled from the cellphone of a young man who, seemingly out of the blue, had tried to set a local refugee house on fire.
The young man lived much of his life online, where he slid slowly and privately into extremism. It had begun as a joke. He and a friend would share racist memes to provoke and shock one another. Over time, the shock value wore off and the hate became sincere.