A seventeen-second video shows a dark-haired man rapping his pale knuckles gently below the tinted windows of a silver minivan. He stands back, shoving his hands into the pockets of his puffer coat, his boyish face twisted into a severe expression. The car drives off, and the camera pans to follow it down the suburban Minneapolis road. No words are spoken. Splashed across the screen, a bright red and white caption reads, “ICE was circling a local elementary school. I knocked on their door to have a conversation, but they ran away instead.” The man is Matt Little, 41, a...