A lot of things would be easier without religion.
Not that I agree with what stars2heaven said, but Stalin and Pol Pot killed people because they were dictators. They eliminated any idea or organization that stood in the way of their power or influence. Atheism wasn't the cause, since atheism isn't a philosophy, Stalin was a nihilist that only believed in his own glory. It's sort of dishonest to say that of Stalin had been a Christian, rather than an Atheist, he wouldn't have killed as many people. Hitler was a Roman Catholic (apparently he converted to Protestantism), his anti-semitism grew from his Christian upbringing and the anti-Semitic views of the time. After all, Jews did kill Christ.
If Stalin hated all Christians, then why did he ally with Hitler's Germany in the early days of the WW2? Atheism didn't kill Stalin's people. I'm fairly sure Stalin killed a lot more Jews than Christians, but he mainly killed people who defied him or stood in his way. It wasn't philosophy, it was authoritarianism. As for Pol Pot, I don't know much about his personal life.