Read the whole thing of course--including the comments, some of which are really excellent. What interested me was this:
...he describes five key vectors or values of psychological morality: (1) care/harm, (2) fairness, (3) loyalty, (4) authority, and (5) sanctity. Haidt finds in his research that self-described “conservatives” tend to value all five vectors of morality (as he defines them). Liberals, by contrast, place a high value on “care” and “fairness”...
One might think this is all purely theoretical but some science was added:
...Haidt reports on the following experiment: after determining whether someone is liberal or conservative, he then has each person answer the standard battery of questions as if he were the opposite ideology. So, he would ask a liberal to answer the questions as if he were a “typical conservative” and vice-versa. What he finds is quite striking: “The results were clear and consistent. Moderates and conservatives were most accurate in their predictions, whether they were pretending to be liberals or conservatives. Liberals were the least accurate, especially those who describe themselves as ‘very liberal.’ ...
Conservatives and moderates can predict the kind of answers liberals will make because they have all the same tools, in addition to others which are lacking in liberals.
This explains very well an observed tendency one sees all the time:
In short, Haidt’s research suggests that many liberals really do believe that conservatives are heartless bastards–or as a friend of mine once remarked, “Conservatives think that liberals are good people with bad ideas, whereas liberals think conservatives are bad people”–and very liberal people think that especially strongly. Haidt suggests that there is some truth to this.
In fairness, I've seen the above formulation going in both directions. While I don't want to rule-out the possibility of there being some small number of genuinely evil people in the world, a safe rule is that if you think someone is evil, you are probably thinking about an issue in a simple-minded way.
Secondary observations: The side that can understand their opponent's viewpoint can be persuaded by it. The other side cannot understand the opposition's positions (except by assuming bad faith) and so are never persuaded. This would present a distinct disadvantage to the conservative side. It is an opportunity for a larger game though: If you can show how the other factors (which liberals are currently blind to) matter, then you might just plant a seed. A kind of broader-understanding-of-things seed, which might allow them to grow into a conservative.