" This is how democracy dies. The great Athenian historian Thucydides showed us twenty-five hundred years ago what a democracy looks like in its death throes. It is not pretty. The following passage, from Book III of The History of the Peloponnesian War, discusses the civil war in Corcyra, Athens's key democratic ally, whose conflict with Corinth was one of the main events that propelled the Hellenistic world into war:
'Words had to change their ordinary meaning and to take that which was now given them. Reckless audacity came to be considered the courage of a loyal ally; prudent hesitation, specious cowardice; moderation was held to be a cloak for unmanliness; ability to see all sides of a question, inaptness to act on any. ... The advocate of extreme measures was always trustworthy; his opponent a man to be suspected. ... To forestall an intending criminal, or to suggest the idea of a crime where it was wanting, was equally commended until even blood became a weaker tie than party, from the superior readiness of those united by the latter to dare everything without reserve. ... Meanwhile the moderate part of the citizens perished between the two, either for not joining in the quarrel, or because envy would not suffer them to escape.' ...
One constant in Thucydides's analysis is that democracy stops working when its people divide into tribes and treat each other as enemies. When this happens, the structural mechanisms of democracy itself amplify the enmity by giving any majority, no matter how slight, the power to inflict whatever torments its members can dream up on the minority - which they invariably do because this is how one treats one's enemies. Furthermore, intractable divisions within a society can be exploited by external forces to hasten that society's demise. People who consider their fellow citizens their enemies tend to be less discriminating about whose citizens they consider their friends. "
― Michael Austin , We Must Not Be Enemies: Restoring America's Civic Tradition