At the deepest level, we make decisions based on our self-worth. If we feel good about ourselves we will make decisions that we hope will continue the trend. If we feel bad about ourselves we will try to alleviate those negative feelings in some way. This is a very general statement, but it has very specific effects.
If our parents were extremely negative, fear-inducing or abusive, we grow up with very negative feelings about ourselves. Nobody can live that way, and everybody attempts to feel better about himself or herself, in both negative and positive ways. One way of dealing with negative feelings is through identification with a group that brings out positive feelings. If you are a part of this group--which must be a superior group to compensate for your feelings of inferiority--you can assume its virtues for yourself.
When your football team wins, you feel proud. When a member of your religion distinguishes himself, you feel good about yourself. When your presidential candidate wins, you rejoice at this nation-wide stamp of approval of your political opinions. Our ideologies are tribal, our politics are tribal, our churches are tribal, and most of all, we belong to that first tribe of family, who taught us to borrow self-respect when we have none of our own.
To be part of a tribe is constant work, because tribes define themselves by shared practices and kinship and thus must define those who don't share kinship as The Other, the not-us, the threat to the homogeneity of shared thought. Thoughts (and therefore decisions) are not based on fact, reason and logic, they are based on how well the authoritarian adheres to tribal rules and practices.
Megan McArdle, defender of the indefensible, is rising through the ranks to the top of the right's intellectual ladder by defending Goldman Sachs, bankers, and income inequality. True, it's a short ladder that even Jonah Goldberg could heave himself up, but she's still accomplished a great deal in conservative circles. The bad thing about tribalism is that quality isn't a requirement for advancement and you end up dominated by hacks. When your back bench consists of the McArdle/Goldberg mutual admiration society, I'm guessing that the party of Standing Athwart History Yelling Stop isn't gong to be going anywhere for a while.