thucydides

Thucydides, on the degeneration of society wrought by war.
These words discuss the general loss of civil discussion caused by entering into war. I would extend that into a figurative war...wherein the purpose of debate becomes only to achieve a victory over the other party.

Or, perhaps, we can think of the "war," that has the below enumerated effects on social rhetoric, as the elongated and ultimately quietly mummering wars that we have lived under for decades...the cold war ,the war on drugs, the culture war, the war on terrorism effected under Bush I, the war on terror began after September 11 2001. In this respect, there has always been something to which rhetoricians can point and accuse the other side as not uniting against, not defeating, not being patriotic against what is purportedly a known enemy. This object of war, then, becomes a flexible straw thing upon which base rhetoric is hanged. Read Thucydides, speaking of public deliberation in Athens during the war with Sparta (it lasted 30 years):

Practically the whole of the Hellenic world was convulsed, with rival parties in every state--democratic leaders trying to bring in the Athenians, and oligarchs trying to bring in the Spartans...To fit in with the change of events, words, too, had to change their unsual meanings. What used to be described as a thoughtless act of aggression was now regarded as the courage one would expect to find in a party member; to think of the future and wait was merely another way of saying one was a coward; any idea of moderation was just an attempt to disguise one's unmanly character; ability to understand a question from all sides meant that one was totally unfitted for action. Fanatical enthusiasm was the mark of a real man, and to plot against an enemy behind his back was perfectly legitimate self-defense. Anyone who held violent opinions could always be trusted, and anyone who objected to them became a suspect....As a result...there was a general deterioration of character thoughout the Greek world. The plain way of looking at things, which is so much the mark of a noble nature, was regarded as a ridiculous quality and soon ceased to exist. Society became divided into camps in which no man trsted his fellow.

Words had to change. I take away, from this, that war (amongst other things, I'd argue) causes defensiveness and the loss of a willingness to be vulnerable. This lesson, really, isn't new. The more defensive we become, the more closed and harsh our rhetoric gets. To get anywhere in public discussion, we need vulnerability.

Another historic note, jumping forward a few centuries from Thucydides: Early Christians, of course, considered themselves Jewish. And Judaism, in the first century, had a great deal of sects. It was only after Rome really closed in that Judaism tightened up and what would become known as Christian belief was no longer allowed within the fold. I find something similar, here. The closing off resulting from a defensive posture.