Ibn,
Stalin is the one dude the religious deluded always draw to to invalidate atheism.
It is not logical to suggest that Stalin did what he did because he was an Atheist. He had a moustache, does that mean all moustached men are murderers. He did not murder in the name of Atheism. However, there is no doubt he committed atrocities.
NO RELIGION on the other hand- hmm lets see- No Crusades, No witch hunts, no Indian partition, no Israleli/Palestinian wars, no Serb/Croat/Muslim massacres, no persecution of jews as 'christ killers', no northern Ireland troubles, no public beheadings of blasphemers, no flogging of female skin for showing an inch of it, no 'honour killings', no Taliban blowing up artefacts, no 9/11 and the list goes on and on.