Going back in time, we have the 1960s violence by hippies, union violence, and on back until Democrats owned slaves.
I read the late Judge Robert Bork's book, Slouching Towards Gomorrah in horror through the opening chapters. The utter violence and contempt-laden obscenity of the leftist 60's protesters, witnessed first-hand by Bork, was horrific and nightmare-inducing. Trees doused in gasoline and ignited and an ROTC building burned down (Kent State); college administrative offices being overrun and taken over (occupied) by hippie students and non-student interlopers; books and personal paper rummaged through and burned; college town business districts terrorized and looted/burned/bombed; etc. etc.
That time was a window into what we were looking at as our future if we refused to combat it. Unfortunately, we didn't, or didn't with enough vigor.