The people at Jonestown studied this movie
The people at Jonestown in Guyana watched, studied and analyzed this movie a mere five months before the mass suicide-murder of 918 people on November 18, 1978. I found this information in a journal written by one of the residents at the time, Edith Roller (who did not survive). http://jonestown.sdsu.edu/?page_id=35697
I'm guessing that Jim Jones viewed himself as the persecuted "leftist" leader and used this film as part of his propaganda to convince his followers of his delusional belief that the CIA was out to get them because of their successful commune.