A screamer, explains author Samantha Power at the opening of this conscience-rocking documentary, is “somebody whose defenses and alibis somehow melt away and they actually process what a genocide is.” That’s a pretty lame connection between moral outrage and System of a Down’s vocal style, but the film has some sturdier links. Screamers follows the Armenian-American nü-metal quartet on tour, but it wasn’t made just for System of a Down fans—it spends more time analyzing historical events than observing high jinks on the band bus. Director and co-producer Carla Garapedian, who is also Armenian-American, provides a quick but reasonably thorough account of the systematic murder of an estimated 1.5 million Armenians by Turks between 1915 and 1923 and connects that bloodbath to better-known atrocities in Sudan, Rwanda, Bosnia, and Cambodia, as well as the Holocaust. (Planning his infamy in 1939, Hitler remarked, “Who, after all, speaks today of the annihilation of the Armenians?”) The members of System of a Down, whose heavy but baroque rock suggests a contemporary Queen, are not casual do-gooders. The group’s lyrics address Armenian genocide, and images of it are projected behind the musicians at concerts. Frontman Serj Tankian’s grandfather survived the carnage, and in the documentary Tankian is shown at the Capitol, trying to sell then Majority Leader Dennis Hastert on an official U.S. declaration deploring the genocide. When not treating the massacre as personal history, Tankian tends to put it in rabble-rousing terms: “Time to make the Turkish government pay for their fucking crimes!” he announces from the stage, without explaining how that could be arranged. Power, a Harvard professor who wrote A Problem From Hell: America and the Age of Genocide, serves as the resident grown-up; her commentary, although fragmented, is more concerned with the ongoing lessons of past horrors than with retribution for them. The film doesn’t favor her views over Tankian’s, but it does gradually shift its focus away from the band, implicitly conceding that reasoned discourse is more effective than screaming.