I think you are correct about the political violence being higher in 20th century USA. For anyone doubting it, just look at the black experience in the south during the civil rights movements. Where I am concerned is that the violence we are seeing today from the federal authorities is being endorsed by the federal government. In fact all leadership is doubling down and turning up the rhetoric whereas during the 50's and 60's it was the federal government stepping in if things got out of hand. With what is happening today, who will step in to cool things down?
I agree that violence from federal agents, who then get backed up by the federal government, is extremely concerning. Nonetheless, it's not a new development; feds have been involved in innumerable fatalities that never got properly investigated by leadership going all the way back to the inception of the FBI.
One example of many, Lon Horiuchi was charge by the state of Idaho for the murder of Vicki and Sammy Weaver. His case was then moved into the federal system which promptly dismissed it and made him a free man. Even today,trying to discuss this case gets bogged down in irrelevant debate about the validity of Randy's political beliefs, which shouldn't matter a single wit.