People tend to think that religions are killing each other over ideology but forget to mention anything that has nothing to do with religion that is also ideology or pure greed that made giant terrifying wars happen.

Religion is a set of ideologies that form your life style and decision making processes. It has little to do with a deity and more to do with how you live life and make decisions and treat people and such.

Many examples such as this on reddit illustrates that a differentiation has been made between theists and atheists in terms of violent tendencies and reasons for doing things vs the actual tie which is ideology and disagreement.

Why do we fight for something so passionately? We fight for ourselves or others. If we fight for others we are trying to save the other parties from a bad life. If we are fighting for ourselves, logic does not matter as only the well being of those being selfish matters to those that are selfish. They seek alliances with similar folks but there is no honor among thieves. This means that if you are willing to lie, cheat, steal, and kill someone else, you are willing to probably do it to anyone. The propensity has been shown and that propensity is what matters most.

A group will kill and protect for its group at times but this is an effect of protecting what they feel is good for their group and that their group is entitled to. The entitled to part matters. This more or less means that it is ok normally to fight to protect your well being as long as your well being is not being interrupted due needing to be punished or something similar.