Moral foundations are evolved psychological mechanisms of social perception, intuition, reasoning and awareness. They’re the color receptors of the moral mind. They’re also the tools in the “toolbox” of the social animal that make possible “the greatest miracle” of cooperative society; in this sense they’re the primary colors of fundamental human nature.
This explains Haid’t findings that conservatives understand liberals better than liberals understand conservatives, and it explains his observation that conservatives understand human nature better than liberals do (also here).
For two and a quarter centuries the conversation between liberals and conservatives about social issues has been like a conversation between color blind people and fully sighted people about rainbows, in which the socially color blind liberals think the fully sighted conservatives are immoral and/or dysfunctional because they see moral colors that “everyone knows” just aren’t there, and the fully sighted conservatives think the color blind liberals are naive and short sighted for NOT seeing moral colors that “everyone knows” ARE there. When half the tools of social cognition are external to, and beyond the reach of, one’s awareness as is the case for liberals one is left with no logical alternative but to conclude that people who think differently must be, can only be, afflicted with some sort of mental, social, or psychological discourse. That being the case it’s only natural for liberals to feel not only justified, but morally bound, to exclude such people and their ideas from “polite” civil discourse. Across the aisle, it explains why conservatives think liberals are naive, childlike, and overly simplistic in their perceptions of, and thinking about, human nature and social issues. This explains the old saying that conservatives tend to see liberals as good people with bad ideas, whereas liberals tend to see conservatives as bad people.
It also explains the eighteenth century cult of reason and the guillotine, and their twenty-first century counterparts of the culture of victimhood, microaggressions, trigger warnings, and the legal system; the aim of all of which has been, and still is, to deny access to civil discourse, and even to livelihoods, of people who don’t think “correctly.”
This is the elephant in the room that facts and evidence and reason and the scientific process prove is there, and that liberalism exists in denial of, that we’re going to have to talk about and address if the human animal is ever going to have any chance at all of fully understanding itself, and through that understanding finding common ground, and from that common ground possibly answering “Yes” to Rodney King’s question, “Can we all get along?”