The New York Times has an interesting excerpt from Jonathan Haidt’s book, “The Righteous Mind: Why Good People Are Divided by Politics and Religion,” arguing that much of the current political polarization is rooted in tribal conceptions of “sacredness.” As Haidt says:

Self-interest, political scientists have found, is a surprisingly weak predictor of people’s views on specific issues. Parents of children in public school are not more supportive of government aid to schools than other citizens. People without health insurance are not more likely to favor government-provided health insurance than are people who are fully insured.
Despite what you might have learned in Economics 101, people aren’t always selfish. In politics, they’re more often groupish. When people feel that a group they value — be it racial, religious, regional or ideological — is under attack, they rally to its defense, even at some cost to themselves. We evolved to be tribal, and politics is a competition among coalitions of tribes.
The key to understanding tribal behavior is not money, it’s sacredness. The great trick that humans developed at some point in the last few hundred thousand years is the ability to circle around a tree, rock, ancestor, flag, book or god, and then treat that thing as sacred. People who worship the same idol can trust one another, work as a team and prevail over less cohesive groups. So if you want to understand politics, and especially our divisive culture wars, you must follow the sacredness.

Haidt goes on to provide compelling examples on the left and right, and observes,

This is why we’ve seen the sudden re-emergence of the older culture war — the one between the religious right and the secular left that raged for so many years before the financial crisis and the rise of the Tea Party. When sacred objects are threatened, we can expect a ferocious tribal response. The right perceives a “war on Christianity” and gears up for a holy war. The left perceives a “war on women” and gears up for, well, a holy war.

it’s a useful model, as long as it’s not leveraged in service to false equivalence. As Haidt concludes: “The timing could hardly be worse. America faces multiple threats and challenges, many of which will require each side to accept a “grand bargain” that imposes, at the very least, painful compromises on core economic values. But when your opponent is the devil, bargaining and compromise are themselves forms of sacrilege.”