It usually is: "I am doing it in the name of DOGMA". Yes dogma is an excuse for war. Because Dogma is made as any other human law, so it can serve as The law. It is conceived by the human mind, not revealed. All the wars have some kind of legal pretexts (like "this land was ours based on the piece of ancient paper we found under a pile of camel excrements and carbon dated it to be older than this country's declaration of independence and hence we should invade it"). Replace the text in the parenthesis with any issue any dogma can provide and you've got yourself a pretext for war. Honestly i have rarely heard of a "sincere" wars, that is where people went on formed an army and started to kill their neighbors because they wanted their land, their wealth or simply they hated their guts. Romans had some degree of sincerity, in the sense that wars were almost always political, without needing pretexts. Looking back didn't that built some respect? So again, yes dogma is an excellently fit pretext for war. Dont confuse it with religion. For example its not a revelatory experience of some pope that drove the crusaders to act like barbarians, but some dogmatic view that christians should politically rule the Jerusalem. Thats all. However the pretext was superbly motivating for the educated warriors of the time. Nowadays its all the same. Again.