We’re lousy at challenging our own beliefs, but we’re good at challenging each other’s. Haidt compares us to neurons in a giant brain, capable of “producing good reasoning as an emergent property of the social system.”
It is called being in a familiar place. Ever tried to give directions to someone. You know the turns, but what about the street names? When I am very familiar with an area, such as my neighborhood, I can easily tell people “first right, second left”, but am very hard pressed to name the streets. I do not need to know them. I just need to know the turns.
Thus it is with our own beliefs. We already know them, so we do not have to name them. But when telling someone how to get from an unknown place to our place, we make sure they know the names as well. We know the arguments against what we do not believe, but having gone over the same road so many times, we may forget the arguments that got us there in the first place.