I have long argued, based on my own experiences, that the study of other religions is one of the best ways to lose your faith in the religion you were raised with. Brian Jay Stanley makes a similar point in this essay, part of a larger piece, in Sun Magazine.
Before college I was a skeptic and rationalist toward every religion except my own, Christianity. Like most of humanity, I had believed the religion I’d heard first, and on its authority dismissed all the religions I’d heard second. Seeing Muslims wearing turbans or Hindus bindis, I thought the oddity of their customs proved the error of their beliefs. Studying all faiths in one class in college, however, I saw my religion from the outside and realized that the rites of my Sundays — warbling choirs and smocked babies dipped in silver fonts and bread as the body of Christ — were as curious as what I had disparaged as myths. In class discussions I sometimes unwittingly revealed assumptions that I thought were axioms, and would read surprise in the eyes of a Hare Krishna or Bahai. My notion of normal was an accident of my birth and upbringing. Whomever I saw as strange saw me as strange. I had raised a doubtful brow at Buddhists bowing to golden statues, even as I prayed weekly to a crucified first-century Jew, not realizing that either all religions are bizarre or none is.