Democracy is, indeed, an anomaly. Our minds are tribally hardwired. Sports is a good example of a relatively benign example of the tribal impulse. Good teams form tight tribal bonds and often develop a fanatical following. Both they and their fans exhibit an intense dislike for opposing teams. It is power politics turned into a game.
To function effectively democracies are compelled to foster cooperation with internal opponents — very difficult as you can see in America today. This is why democracies so easily decay into dictatorships or split apart in revolutions.