I agree. That’s why the question “why don’t religions get along”. We can understand the individuality of political power, but that is not what we are discussing. Communism is not a religion. Atheism is not a causal belief system, it’s very nature is secular.
I think people of differing religions can and do get along. It is not religions, in most case, that have laws, law enforcement and militaries. That’s the realm of nations. Nations go to war. Religions are a set of beliefs concerning God. Communism is a set of beliefs concerning social order. The Communists were willing to kill millions for their set of beliefs. They were atheist. So atheists can be just as responsible for war and killing as theists.
I would say that theism is not a causal belief system either. Just as atheism is a belief that there is no God, theism is a belief that there is a God. It’s the ideology and the set of beliefs that go along with those two positions that will define what the people are willing to do and what kind of people they strive to be.
In my view you are wrong to say that atheism is a belief that there is no god. Atheism is a lack of belief that a god exists. That is completely at odds with a belief that there is no god. One does not have to believe anything concerning god to be an atheist. All we have to do is reject a claim that as no evidence, which is what we do. It is not necessary to believe anything regarding the existence of a god. Rejecting the claim is all that is neessary.