Discussion 1 to Meditation 596
Religion is far from a weak instinct
I don't think you are far off with your theory, but not "dead on" either. Religion is far from a weak instinct, and most people will never in their lives overcome it even once. Also, think about people willing to die for their religion. Most people wouldn't die to, say, have sex, and we all know how strong an instinct the mating urge is.
I think religion helps establish the tribal identity. It sets you apart from other tribes, and when you conquer your neighbours you can force your religion down their throats to keep em subdued (since, obviously, they are not god's chosen people and as such they stand below you) Very useful, all in all. Except that western civilization's tribal age is long past...