Tonight on PBS, the brilliant documentary “1971” will be shown on the Independent Lens series. In 1971, a group of ordinary citizens broke into a small FBI office in Pennsylvania and shared with the world their findings on COINTELPRO, the FBI’s illegal surveillance program. It led to the first-ever oversight hearings on the FBI and paved the way for Daniel Ellsberg, Julian Assange, and Edward Snowden. And yet, the FBI never identified them. Now, they tell their story publicly for the first time.