The historical term for this kind of anxiety is “Brown Scare” — an inordinate fear of a vast far-right conspiracy, which resembles the anti-Communist panics of our past. As the historian Philip Jenkins wrote in 2009, Brown Scares no less than Red Scares recur throughout American history. They fasten on real-enough phenomena, from homegrown fascist sympathizers in the 1930s to the militia movements in the 1990s, but then wildly exaggerate both the danger these extremists pose and their ties to the conservative mainstream.

In the ’30s, Jenkins noted, this mentality inspired the persistent media-fed fear that “the U.S. was about to be overwhelmed by ultra-Right fifth columnists, millions strong, intimately allied with the Axis powers.” In the ’60s, it persuaded many liberals that Dallas’s right-wing fever was somehow responsible for John F. Kennedy’s assassination even though the president’s actual assassin was a Communist sympathizer. (This idée fixe persists to the present day.) After the Oklahoma City bombing, it led many people to tar the entire militia movement as terrorist, not just extremist, and then to conflate the militias (this was one of Bill Clinton’s defter moves) with the mainstream small-government right.

Our own era’s Brown Scare followed a similar pattern. Early in President Obama’s first term, a Department of Homeland Security report predicted an increase in right-wing extremism, citing real threats but also employing “a definition of extremist so broad,” Reason magazine’s Jesse Walker noted, that “it seemed to include anyone who opposed abortion or immigration or excessive federal power.”