I organize with many religious socialists. It is a strange thing to wrestle with, for sure, since we place ourselves in a Marxist tradition, which most always concludes atheism as the only path. I will say that I think religion under capitalism and religion under a different and/or socialist world structure would be completely different things. Capitalism binds religion, poisons it, and makes it reflect capitalist tendencies. Religion under socialism or another alternative could/would free the individual, possibly diminish whatever it is that attracts them to their religion, or give them the open-air to explore their spiritually more meaningfully. It's frequently the institution of the religion that is more problematic than the participant or the core values of it.