While it is true that Joseph Stalin (1879-1953), Mao Zedong (1893-1976) and Pol Pot (1925-1998) were all atheists, this is not the only thing they have in common. They were also men, political leaders and communists. Merely citing common denominators does not establish the cause of their actions. It is important to consider what was the main driving force in their committing atrocities against their own people.
One could make a valid claim that since Stalin attended a Russian orthodox seminary (from 1894 to 1899) as a teenager in Tiflis, the dogmatic black or white outlook of the world influenced his subsequent actions. As the historian Alan Bullock in his book Hitler and Stalin: Parallel Lives (1991) explained: