Thanks for your thoughtful response. You certainly have gotten to the heart of the matter. There is a difference in world view. Miss O'Connor believes that we arrive on the scene already marred by original sin, and that as we grow and mature, we make more of a mess of it.
You believe otherwise. And if you're correct, then her fiction is worse than grotesque, it's morally odious.
However, Miss O'Connor might cite in her favor the fact that much evil is done in the world by human beings. They are not the actions of good, straight, and already whole human beings.