Make a list of your top ten favourite works of fiction. Now remove from your list all the books that contain an element of the mythological, magical, supernatural, paranormal or religious. What you have left are the books that people would read if they truly believed that the impulse to believe in the transcendant is purely a function of our minds without any possibility of there being anything that we call transcendant. Even most of Philip Pullman's books would not be read.
It's not just religion that comes out of this part of our mind, most works of creativity are born from the same part of our mind (not brain) that gives us the religious impulse. But the scary bit is that it is also that part of us that allows us to imagine and enjoy art. We would no longer do so if we completely believed our enjoyment was due only a biological function. We would be cynical and would not be able to suspend our belief, a major requirement for the enjoyment of much literature. Life without at least the possibility of the gods et al would be very boring.
I'm sure it would be possible for a writer to cynically write a "magical" book without any subconscious belief in the possibility of the magical. It would be enjoying reading them that would be the problem. It would be like reading a biography about Sarah Palin in which she is a nice, sane person who loves animals and would always put other people before herself. Once you know and truly believe "the truth" about something you cannot imagine things a different way. You reaction would be "That's just plain silly."
It's absolutely right to tell people that the religious impulse can be traced to a specific part of our brain, if it is true. What is wrong is telling people that this means there can be no possibility of something real to feel religious about. I think it's morally worse than telling people they have to believe in god(s). Anti-religionists believe (if that is the right word) that getting rid of the religious impulse would lead to more evolved, "better" human beings. I think it would destroy us, or at the very least it would destroy those bits of us that both religious people and atheists hold to be good.
I am not defending any religion here. I'm defending our right to believe in anything we can imagine, because it is that which makes us happy. You take that away and we would never be happy, we would just get pleasure from satisfying our biological lusts.