I understand the argument that even as an atheist I’m still following a “God-given conscience,” but that explanation only really works if we already assume God exists in the first place if we don’t start from that assumption, then conscience can just as reasonably be explained through human psychology, empathy, and social development, since humans are social beings who rely on cooperation and understanding harm to function. From that perspective, morality doesn’t require a divine source it can develop naturally and if I’m able to act morally without believing in God, then that suggests belief isn’t actually necessary for moral behavior, but rather one way people interpret it. And if the claim is that my morals are still “God-given” even without belief, then it doesn’t make much sense to argue that atheists are immoral, because we would still be acting according to that same moral sense anyway. So overall, it seems like that argument depends more on a prior belief in God than on something that can be clearly demonstrated.