The practice of civility is important to democracy. In his book, "Civility: Manners, Morals and the Etiquette of Democracy," Stephen Carter defines civility as "the sum of the many sacrifices we are called to make for the sake of living together. ... We should make sacrifices for others not simply because doing so makes social life easier (although it does), but as a signal of respect for our fellow citizens, marking them as full equals, both before the law and before God."
Respect makes cooperation in the common good possible. Civility acts like grease in the democratic machine; disdain is sand thrown into the gears. But civility is also a direct reflection of our belief in human equality. Even people we vehemently disagree with on the largest issues possess a democratic value equal to our own. Carter argues that this recognition does not preclude "passionate disagreement," but it does require "civil listening" -- and I'd guess it forbids referring to strangers as a..holes and hoping for their death.
So civility has an unavoidably moral component. The proper treatment of others conveys regard and demonstrates self-control. Rudeness sets out to dominate and humiliate. This is not only true in politics. "Precisely because rudeness is quite common," says philosophy professor Emrys Westacott, "it is not a trivial issue. Indeed, in our day-to-day lives it is possibly responsible for more pain than any other moral failing." Verbal violence can leave people smarting for days, or scarred for years, or pushed like a vulnerable junior high-schooler toward suicide. Such hostility is broadly and correctly condemned. Why does politics seem to numb this rudimentary moral sense?
The answer, of course, is the infectious nature of incivility itself. Every excess provides the excuse for greater and opposite excess -- a search for more vicious put-downs and more startling obscenities. Avoiding this escalation is one of the primary challenges of the schoolyard and one of the important attributes of a citizen. Everyone has grievances; fewer have the courage of manners. All of us need more of it.