We are in a particularly tribal moment in American politics in which “the enemy of my enemy is my ally” is the most powerful argument around.

John Tooby, the evolutionary psychologist, recently wrote that if he could explain one scientific concept to the public it would be the “coalitional instinct.” In our natural habitat, to be alone was to be vulnerable. If “you had no coalition, you were nakedly at the mercy of everyone else, so the instinct to belong to a coalition has urgency, pre-existing and superseding any policy-driven basis for membership,” Tooby wrote on Edge.org [5]. “This is why group beliefs are free to be so weird.” 

We overlook the hypocrisies and shortcomings within our coalition out of a desire to protect ourselves from our enemies.

Today, the right sees the left as enemies — and, I should say, vice versa. ...