You make think it flawed but it actually makes perfect sense.
Requiring strict adherence and zero tolerance of other beliefs gives maximum chance of numbers building up quickly, and allows nearly any behaviour to be justified in pursuit of these aims.
A religion that doesnt require anything out of you, that doesnt require you to fight for your beliefs, that allows all other points of view to co-exist and even prosper, isnt going to win the evolutionary fight for survival and dominance.
Life is not fair, nature is cruel indeed. Smart people worked out a long time ago that they can get other people to do almost anything in the name of a higher cause. All religions around the world require effort and input from their followers.
