The question of marxist atheism is very problematical at this point. Looking at the new atheists we get a glimpse of the way the original secular humanists, among them the early marxists, spoiled their own atheism with a very narrow take on religion and the spirituality. This is not a gesture to re-introduce ‘god’ into a leftist perspective, but simply a warning that atheism spoiled the communist movement and ended in the worst case: complete psychopaths running amok throughout the movement. It didn’t have to be that way, and atheism as such is not the problem, until it is the problem.
A better solution is to backtrack to the Kantian period and its critique of metaphysics, including the the ‘realism’ of the positivists, in order to transcend the useless dilemmas of theism/atheism: they are two of a kind and simple play back and forth.
The history of religion is very complex and complete erasure of the whole legacy is simply another form of fanaticism.