Even if a person considers all "holy books" to be 100% BS he's still so brainwashed that he follows the basic rule, which is to believe and obey without exception. He might toss the belief in deities overboard but he will create his own "god" that he will believe in and obey without exception. For instance, people willfully do that in times of national crisis when their leaders tell them what a bunch of scum the folks over the hill are. So they gladly suit up and pick up clubs to go smash their brains even though they have no first hand experience with the people over the hill. They have elevated their leader to "god" and believe what he says without exception. If he says to roast them alive they will do it without a second thought. That's exactly what the characters in the Bible and in the Koran did.
Only idiots think that an invisible celestial deity holds conversations with people.
Only idiots think that an invisible celestial deity holds conversations with people.