As it happens, George Floyd died exactly 100 years and 40 days after Alessandro Berardelli and Frederick Parmenter were shot to death in a payroll robbery in Braintree, Massachusetts. These men have little in common with Floyd save that none of them deserved to die and that their respective deaths set off worldwide demonstrations orchestrated out of the very same playbook. In the 1920s, communists had to erase some immediate history — namely, the fact that a pair of Italian anarchists murdered Berardelli and Parmenter in cold blood. The evidence that the anarchists, Nicola Sacco and Bartolomeo Vanzetti, killed the...