In 1964, an Ohio Ku Klux Klan leader named Clarence Brandenburg told a Cincinnati-based reporter that his hate group would soon be holding a rally in a rural area of Hamilton County. In the filmed portions of that rally, which later became the focus of legal prosecution, robed men, some with guns, could be seen burning a cross and making speeches, infamously demanding “revengeance” against blacks (they used another word, of course), Jews, and the white politicians who were supposedly betraying their own “caucasian race.” They also revealed a plan for an imminent march on Washington, DC.
In American First-Amendment jurisprudence, Brandenburg’s name is now a byword for the test that is used in assessing the validity of laws against inflammatory speech—especially speech that can lead to the sort of hateful mob activity that played out at the US Capitol last Wednesday.