There are the YouTubers such as PewDiePie, the Swedish gamer and vlogger who has shown Nazi videos while metaphorically arching his eyebrows. Viewers are meant to get that it’s a joke: “I know my audience understand that and that is why they come to my channel,” he has said. There are discussion boards and chat groups. You can start with Reddit or the comment sections of Breitbart, where many of the white supremacist references are coded or disguised. If that begins to seem tame, there is 4chan or 8chan or, where the conversation is much more open.

Eventually, you can wind up living in a world in which the vilest forms of racism and hatred seem absolutely normal, in which mass murder is amusing and compassion is for the weak-minded. You can even wind up reading the Daily Stormer, which gets its name from the Nazi Der Sturmer , also once known for its “humorous” caricatures and cartoons. On Friday morning, the Daily Stormer’s home page marked the mass murder carried out at mosques in New Zealand with a long rant making fun of the anticipated “mainstream” reaction: “No one cares about this, and if you are pretending you or other people care about it, you’re simply lying.”