Stewart Rhodes was living his vision of the future. On television, American cities were burning, while on the internet, rumors warned that antifa bands were coming to terrorize the suburbs. Rhodes was driving around South Texas, getting ready for them. He answered his phone. “Let’s not f**k around,” he said. “We’ve descended into civil war.” It was a Friday evening in June. Rhodes, 55, is a stocky man with a gray buzz cut, a wardrobe of tactical-casual attire, and a black eye patch. With him in his pickup were a pistol and a dusty black hat with the gold logo...