I mean my counterargument here is that religion didn't cause the Crusades (or a reskin thereof); the existence of an authority able to push the European nobility in the same direction did. You either remove that authority and get limitless endemic conflict or reskin that authority to make it non-religious and get different-looking conflict instead, and neither of these options are an upgrade over the Crusades in terms of amount of violence. Which is to say: Christianity took a whole host of potential conflicts and made some of them reality; it didn't create conflict where none would've existed otherwise. For example, the English and French had been done Crusading into the Holy Land for only a few decades when the Hundred Years' War hit.