As soon as absolute truth is supposed to be contained in the sayings of a certain man, there is a body of experts to interpret his sayings, and these experts infallibly acquire power, since they hold the key to truth. Like any other privileged caste, they use their power for their own advantage. They are, however, in one respect worse than any other privileged caste, since it is their business to expound an unchanging truth, revealed once for all in utter perfection, so that they become necessarily opponents of all intellectual and moral progress.
Bertrand Russell
Has Religion Made Useful Contributions to Civilization
And that, in a nutshell, is the reason that all educated, forward-looking people must inevitably find themselves in opposition to religion: It inevitably, unavoidably, becomes the enemy of “intellectual and moral progress.”