At the bottom of Christianity there are some subtleties that belong to the Orient. Above all, it knows that it is a matter of complete indifference whether something is true, while it is of the utmost importance whether it is believed to be true. Truth and the faith that something is true: two completely separate realms of interest--almost diametrically opposite realms--they are reached by utterly different paths. Having knowledge of this--that is almost the definition of the wise man in the Orient: the Brahmins understand this; Plato understands this; and so does every student of esoteric wisdom. If, for example, it makes men happy to believe that they have been redeemed from sin, it is not necessary, as a condition for this, that man is, in fact, sinful, but merely that he feels sinful. And if faith is quite needed above all, then reason, knowledge, and inquiry must be discredited: the way to truth becomes the forbidden way. -- Nietzsche "The Antichrist"
From my observation, in so far as faith is strong, it obstructs inquiry into truth. It speaks with certainty on matters about which reason and evidence have little to say. And when opposed by reason and evidence it rejects these. It permits no serious doubting or questioning. It gives people what they want: confidence that they know the truth, all the while hiding from them the errors of their beliefs. Faith is a spider that catches even the strongest and most intelligent in its web. And what is most subtle is that they are not even aware that they are caught.