Some might take this to imply that religion is merely organized insanity. But even in highly secularised Western societies, deeply held religious belief is much more common than insanity. And religious belief is not associated with an inability to function in society in the same way that insanity is. Another implication might be that members of a group are more susceptible to mutual deceptions than an individual is to his or her own self-deceptions. But the qualitative difference between religion and insanity suggests that there is something deeper going on here.
Right Humans are intrinsically social animals.
The ability of the group to survive and prosper in a hostile environment far exceeds that of the individual. If individuals in the group have totally incompatible world-views, then it will be difficult for them to hold sensible conversations with each other. It may seem ludicrous that it is preferable for an individual to believe a false proposition just because the social group that they belong to believes it to be true. But nothing in this world is certain. And the cost of being wrong is far greater in the case where you are wrong and the group is right than it is in the case where you are wrong and the group is wrong.