I don't know, if the marxists or anarchists I work with irl ever said that kind of shit, I wouldn't work with them anymore (and we have discussed the topic). Simple as a that. Personally, I'm an atheist and haven't come up against any contradictions between my leftism and my morality or humanism. But if religion is what it takes for people to recognize that killing kids because of some hypothetical future scenario is wrong and will never be justified, then I say keep the churches full.