For white nationalist groups, iconography is a critical means of communication. In many respects, a single symbol — from the swastika of Nazi Germany to the letters “A” and “C” — can express purpose, motivation and meaning more effectively than an essay. Those who study the bewildering array of symbols, phrases, internet memes used by white nationalists say they are also a way to express themselves in public while also providing cover to deny their true intentions. “Symbols are incredibly important from the get-go because having a symbol that is used for multiple things, while being used for one specific...