The posts on social media are of a specific type. They make ominous suggestions that mass massacres are the work of the CIA or FBI. They sell racist, sexist, and homophobic stereotypes. They are looking forward to a “white guy summer.” White nationalists and supremacists are creating robust, masculine networks across social media platforms like Instagram, Telegram, and TikTok, using coded hashtags and innuendo to avoid detection. Thousands of followers are being enraged by their snarky memes and fashionable videos on divisive themes including abortion, weapons, immigration, and LGTBQ rights. The Department of Homeland Security cautioned on Tuesday that such...