Vegetarians turn at the thought of eating the meat of a cow that has died from a heart attack. The disgust that vegetarians experience is not principled. Nor is the greater opposition to homosexuality that people espouse when they are exposed to foul smell. Haidt uses similar such provocative examples to expose chinks in how we think about what is moral and what is not.
Knowing that what we find disgusting may not always be “disgusting,” that our moral reasoning can be flawed, is a superpower. Because thinking that you are in the right makes you self-righteous. It makes you think that you know all the facts, that you are somehow better. Often, we are not. If we stop conflating disgust with being in the right or indeed, with being right, we shall all get along a lot better.