It isn’t unusual for an atheist to have been raised in a religious household and to have grown up living with the assumption that their religious tradition represented the One True Faith. However, after learning more about other religious traditions, this same person may adopt a much more critical attitude towards his own religion and even religion generally, eventually coming to reject not only the religion but also belief in the existence of any gods.
My own experience
In my younger days, when I was in St. John's Boarding School in Ranchi, India, I was surrounded by Jesuit priests and they never wasted a second without reminding me of the ludicrous aspects of Hinduism, viz., the monkey faced demigod cum superman called Hanuman who could fly over the ocean like geese and carry a mountain on his forefinger, an elephant headed Ganesh riding on a mouse, a ten headed demon called Ravan, a goddess called Durga with 8 pairs of hands & a four headed Brahma who is supposed to have created the universe. Same time they didn't forget to drive home the point that Christianity was much saner.
Much later however, I discovered some ludicrous aspects in Christianity as well. Christians are not stupid, but they sure are gullible. Either that, or they have absolutely no common sense when it comes to using logic to analyze their beliefs about the invisible magic guy who gives them their wonderful morals in support of genocide, slavery, subjugation of women, cruelty toward others, and even the stoning of children.
When I had grown up, I posed the following questions to some of my Christian friends who were flummoxed by them:
• Why did the Christian God have to make Eve from a rib, instead of making her from clay (as he did for creating Adam) or simply snapping his fingers and saying abracadabra?
• Why did the Christian God instruct Noah to make an ark, when the Christian God could have just as easily slaughtered all the people on Earth with a magic stroke of his hand? (Wouldn’t that have made his existence less doubtful instead of having to account for the crazy logic problems the ark creates?)
• Why did the Christian God have to create a son to be tortured on the cross as himself, in order to save his own creations from his own wrath?
• Why did the Christian God bother to create distant galaxies millions of light years away that humans will never know about or experience?
• If a boy gets hit by a meteor while walking to school, did the Christian God launch or know about the launch of the meteor and its trajectory thousands of year ago? If the Christian God did know about the meteor, wouldn’t he have had thousands of years of advance knowledge to move the boy out of the impact zone? Was “God’s plan” to launch that meteor all those millennia ago to kill the boy or does the Christian God simply work in mysterious ways?
Either way, the boy died and the Christian God either knew about the boy’s death for centuries or allowed it to happen without saving him.
Those Christian friends were tongue-tied but fortunately they didn't take offense since they were not fundamentalists. So our friendship survived. It occurred to me that Logic and Christianity have no common ground. Same with my Hinduism.
I realized then that all religions were mere fairy tales and have no correspondence whatsoever with reality. All of them claim to be the only true religion but they are so contradictory to each other. I decided that if all of them cannot be true, all of them can certainly be false.
Have you ever wondered why there are so many religions ( Anthropologists say that there are right now 4200+ living religions in the world, around 20 of which are major religions) telling us about the secrets of the universe, life and man but there is only one Universal Science which does the same?
Simply because regarding any one concept, truth can only be one but there can be many lies.