Don't conflate 'religion' with 'arbitrary beliefs'.
Of course within religion there is going to be a lot of 'arbitrary belief', but that's not what it is essentially. 'Parables' etc. are a function of how it's communicated and propagated, ironically, for the 'dumber folks' who 'need something material to believe in' and for whom more abstract concepts don't provide solace.
Religion is a metaphysical perspective of existence, one based on spirituality from which we develop our humanity, morality etc. and none of that is irrational.
Our earliest civilizations often confounded civic norms, civil law, religion, faith, cultural history etc. into the same sphere, from that you get things like the Torah for example (i.e. 'The Law') which is like a legal code, moral code, civic code, national history rolled into one.
Since the Common Era (i.e. about Jesus' time) religion has developed into a more strictly moral and spiritual sphere, less so the core civic stuff, but it still lays at the foundation of all of our institutions ... especially ironically our University system, and partly medical systems depending where you're from.
Our current scientifically materialist 'belief' whereupon we are all merely bags of tiny particles, randomly interacting in accordance with a few 'known forces' - which almost by definition denies the very existence of things which we otherwise believe exist - like 'life', 'love', 'intelligence' etc. is a pretty bizarre bit of irrationality that we somehow don't bother ourselves much about.
Barack Obama along with the majority of our leaders of all kinds are religious and not in the Machiavellian 'fake' sense whereby he 'need to appear religious to get elected', so let's not write them off as idiots and contemplate maybe our crude and easy dismissal is too often misplaced.
Yes, ideological conformism and orthodoxy are going to appeal to certain groups, and that's nice point, but it would be confusing the issue.
And of course ... we all have some truly irrational beliefs.