A stark reality keeps confronting us: Terrible things are being done in the world. The darkest impulses of some people are honed and polished on the internet, in secret. Then those impulses are visited upon us, in violent and sickening ways. One of the most recent such tragedies, as I write, happened in Christchurch, New Zealand, on March 15, 2019, but there might be another by the time you read this. Every time, we all want to know the same thing: What is to be done about this?