If I'm reading this right, religion serves an important social function by establishing nonviolent relationships of dominance and submission through use of religious language, specifically, statement of belief. By signalling your willingness to believe in something that cannot be proven, i.e. faith, you signal your submission to the leader making these supernatural claims. No wonder Paul placed so much emphasis on faith, as it really is the glue that binds the church together. So belief statements are a sort of litmus test, indicating whether you are willing to surrender your better judgment or say you believe something you know isn't true, just to be part of the group, sort of like a psychological gang initiation.
So religion is the human version of wolves biting each other in the mouth and chimpanzees bending over.
Therefore, it stands to reason that religious wars happen because once the leader has established his dominance through the "you can believe me or you can believe your lying eyes" method, he cannot allow his followers to see that another group is unwilling to accept his supernatural claims, even if they are not a direct threat to his group's welfare, because their failure to believe his bullshit is a threat to his leadership.
Religions are only outwardly tolerant of one another when they are forced to co-exist by a higher power, such as a secular government. Left to their own devices, they must tribalize and conflict in order to survive. Different beliefs are, by definition, a direct threat to the cohesion of the group.
So take something like belief in UFOs or Bigfoot, which can become a sort of religion for some. I have long been baffled by the leaders of UFO groups who will ruin any compelling evidence they may have by making further completely outrageous and unproveable claims, thus destroying their own credibility and the credibility of all their evidence. The above language theory would go a long way toward explaining such apparently self-destructive behavior. Although they may outwardly be trying to prove their case, their primary motivation is to establish leadership and attract loyal followers. So proving to the world that UFOs are real is secondary to marking your territory and expanding your harem.
This would also explain the last eight years in America.