True observance of religion involves a personal oneness with God and/or gods, nature etc. Being at odds with our neighbours is not a factor of religion, unless it comes down to the very basic my God is better than your God tit-for-tat. Mostly it comes down to wanting what someone else has got or stopping them from doing something you don�t like, or just generally being a war-mongering psychopath. Which is generally lead by ambition, power, hatred and oppression - and rarely justified by any means. Least of all religion.
If you take religion out of the mix completely, it is likely that various people will still be at odds � they would just find something else to rely on, either by Id, ego, or super-ego.
If AB contribution was to be believed, then the most peaceful religion would be Atheism, wouldn�t it? If not, then perhaps Taoism, although no doubt if you go back far enough there is quite likely to be one or two murky people in their history as well.