The April 13 arrest of Jack Teixeira, a 21-year-old Massachusetts Air National Guardsman, for espionage due to his leaking top secret documents, is yet another stark reminder of the danger far-right extremists pose to national security. But Republicans don’t seem to agree. In a reckless move this past summer, Republicans on the Senate Armed Services Committee (SASC), shut down proposals to root out extremists even as the FBI, Department of Homeland Security and other federal agencies were reporting that white supremacist and antigovernment movements are our number one domestic terrorism threat. SASC Republicans rejected efforts to identify and remove extremists...