When I read "At the mind's limits: Contemplations by a survivor on Auschwitz and its realities" by Jean Amery in college, I was particularly struck by his recognition that a "strong faith" whether held by Marxists, Jehovah's Witnesses, Catholics, etc, conferred survival advantages. Faith provided a shelter against the ravages of Auschwitz as much as working in a covered environment as a machinist or as a physician provided protection against the elements. Faith brought biological benefits, increasing one’s chances of avoiding death, and surviving a little longer.
Faith may make stupid, but it is not without its advantages. Believing that survival is possible in the face of overwhelming adversity makes giving up all the less likely and makes persistence for just a little while longer all the more necessary.
For all the advantages that a passionately held faith may confer, sincerity of that faith shows nothing of the truth or falsity of the object of that faith. I don't deny that there are positive advantages to a fervently held belief when in adverse circumstances. But is it really necessary to insist on that one's faith is true?
Sometimes the radical comfort that a faith held with terrifying firmness affords is necessary for one's physical and psychic survival. This is no argument for the truth of that faith. Morphine is sometimes necessary as well. But that is no argument for compulsory addiction.