socialists used to understand the retarding effect of religion, and the necessity of breaking the power of the church.
there's really no better example than amongst black voters in the south.
the real reason that they won't vote for socialists is that they've been brainwashed by christianity. and, this is the oldest problem on the left - how do you get them away from the church without triggering them and pushing them in further?
the best answer anybody has been able to come up with is to lure them out of the grips of the church by sending them to school. but, it means you need to get into power first.
so long as the church remains the dominant force in southern society, these voters are lost to the socialist cause.