It is very dismaying, but not beyond grasp, why some folks do not understand the viciousness of terrorism. The bottom line is always the same: tribalism. It is also called collectivism — socialist, fascist, communitarian, or any other type of irrational lumping of human beings into groups they have never chosen to join. Any time a terrorist attack occurs, a great many people wring their hands trying to figure out just what is amiss with such barbaric conduct. Be it an IRA, Palestinian, or radical Muslim (suicide) attack, there is the usual acknowledgement that terrorism is horrible and the people...