Robert Grenier says domestic extremists should be treated as an insurgency.

WASHINGTON, DC – JANUARY 06: A large group of pro-Trump protesters stand on the East steps of the Capitol Building after storming its grounds on January 6, 2021 in Washington, DC. A pro-Trump mob stormed the Capitol, breaking windows and clashing with police officers. Trump supporters gathered in the nation’s capital today to protest the ratification of President-elect Joe Biden’s Electoral College victory over President Trump in the 2020 election. (Photo by Jon Cherry/Getty Images)