There is a common misunderstanding about atheism in communist dictatorships such as those found in North Korea, the former USSR, China, etc. This has become more visible recently after the death of the North Korean leader Kim Jong Il. The religious perpetuate the notion that atheism leads to violent totalitarian regeimes. This is a confusion of cause and circumstance, and it's a (disingenuous) tactic religious leaders have intentionally used to mislead the faithful for decades.
These political systems do not arise from some kind of atheist "doctrine" or atheist influence. Often, religion is outlawed (and by that token it could be said that atheism is enforced) because organized religions create their own communities and hierarchies and eventually gain power. Something authoritarian dictatorships dislike.
Throughout the dark ages for example, the catholic church's power rivaled that of any nation in Europe. That's something China, N. Korea, and the former USSR want to avoid, even in small scale. Totalitarianism does not arise from atheism, but religion does complicate things for dictators, for reasons unrelated to the virtues/vices of religion itself. The regime isn't a result of a lack of religion, it is rather that these regimes cannot afford to have their populace worship anything but themselves.