To show that there are natural processes that produce religious belief does nothing, so far, to discredit it; perhaps God designed us in such a way that it is by virtue of those processes that we come to have knowledge of him.
The good news? All you have to do is to believe it.
Am I really arrogant and egoistic just by virtue of believing something I know others don’t believe, where I can’t show them that I am right?
Probably, let's say.
Argument is not needed for rational justification. The believer is entirely within his epistemic right in believing, for example, that God has created the world, even if he has no argument at all for that conclusion.
Ah, of course: the Immanual Can Syndrome.
Freud's complaint is that religious belief lacks warrant because it is produced by wishful thinking, which is a cognitive process that is not aimed at the production of true belief; in Freud's words, it is not reality oriented. But even if it were established that wish fulfilment is the source of theistic belief, however, that wouldn't be enough to establish that the latter has no warrant.
Besides, there's a sucker born every minute. And, as Mike suggested to Margaret, "two to take him".
If my belief in other minds is rational, so is my belief in God.
Unless, of course, it's true.