Yes, religion and violence go together like peas and carrots. Religion is the mortar which cements the architecture of aggression upon which our culture, our society, was built and is maintained. Another neat tidbit is the overall percentage of the Xtian population that's in prison for violent crimes vs. the overall percentage of the atheist population that's in prison. It's fair to say that if Reagan really wanted to pull off a successful "War on Crime" without costing billions to erect the prison-industrial complex, he would have simply filled appointed positions with atheists, encouraged the passing of the ERA, and let the Religious Wrong and their myths and Sky Daddy go the way of the dodo bird. It might not have eliminated crime, but I believe that based on the US Justice Dept. and CIA world fact book stats, an increase in atheism would probably have helped decrease crime.
I agree that Stalin was an atheist, but he was addicted to some religious-like ideologies. For example, he believed, as do most religious militants in historical determinism. Like some militant Muslins Christians, he killed believing he was hastening the end of a predestined Future. Stalin was also like many religious individuals in being prone to accept pseudo-science. For example, he set Soviet agriculture back decades by his forcing Larmarckan evolutionary theory upon Soviet scientists. I would add that Mao also killed millions for the same doctrinaire reasons and flawed acceptance silly pseudo-science. Communism is very similar to religion in many way. The typical skeptical atheist does not believe history to be predestined or would he or she be easily susceptible to dubious scientific theories that fail the peer-reviewed process.