Toughie. I think a LOT of Wars are over religious beliefs - and the Bible supports this as Wars have been going on since Adam was a lad (to coin a phrase) with God's backing. I assume the same in all religions, that Holy men have condoned and encouraged War as a way of ensuring their belief survives and increases.
Theoretically, the number of wars SHOULD reduce if religion was banned, but the fanatics always survive, and they're the danger.