I don't have it in me to exhaustively recap, but Haidt's main point so far is that moral judgment comes from quick intuition, and then we slather reasoning on top of it. Well, not you, of course. You, dear reader, are the epitome of reason, and you have carefully thought through all of your moral and political stances. But everyone else out there--you know, the people less thoughtful than you--they most certainly do proceed from moral intuition and hunches, and put their ethical reasoning in after the fact.
I find this to be useful outside of the moral domain, in terms of understanding persuasion. Too often at work people want to treat the layers above us as some sort of deterministic machine, and they're looking for the consistency so that they can reliably turn the lever and get what they want. But people don't work that way. They have their hot buttons, their emotions, and then also their cooler, calmer side. Different things come into play at different times, and you have to gauge all of those before you can successfully engage in persuasion.