You are confusing corralation for causation and making an argument from ignorance. That, for example, Chairman Mao was atheist has not been shown to be the cause of his actions as a dicatator. If such were true, then it could be said that all Seventh Day Adventists are cult leaders because David Koresh was one.
Additionally, lack of precedent does not indicate impossibility. That you can not imagine how a society, that is not permeated by religion, can be peaceful, joyous, and enlightened does not preclude it from occurring, or having occurred.
So, unless you are planning on proving that the failures in Hitler's Germany, USSR, and Communist China are a direct result of atheism your argument holds no water.