|This page in a nutshell: Being civil encourages others to be civil. Work towards building a civil environment.|
An uncivil environment is a poor environment to work in. It is not conducive to a useful and positive outcome from an already difficult situation. If editors are not staying within the boundaries of civility then they should be warned accordingly, and if they persist, then blocks should be enforced.
If conversations devolve into uncivil rants at each other, how is that helping anyone? Yes, we all believe our side is the right answer and find it difficult to assume good faith of the other parties, but we must force ourselves to as much as possible, and to stay civil. Else we are just a bunch of arguing editors who are doing exactly nothing for improving the site.
Reminding fellow editors of our need for civility is a good thing as it reminds people to stay useful.
Why does an uncivil environment hurt productive editing?
So, why does an uncivil environment hurt productive editing?
Us vs. Them mentality
Let's say I accuse you of "edits bordering on vandalism" about your efforts to NPOV an article. This makes you angry, right? Enough of this sort of thing leads to an Us versus Them mentality, which can prevent any attempt at compromise.
Destruction of nuance
The truth of a situation is often a subtle, difficult to articulate thing. An uncivil environment tends to result in such loud shouting that it becomes impossible to be heard over said shouting, thus making subtle, nuanced positions almost impossible.
If you're in a bad mood, you're more likely to make a mistake. Incivility encourages a bad mood, thus encouraging mistakes.
Erosion of critical thinking
Incivility makes it harder for people to think critically, that is, to evaluate conflicting claims solely on their merits. When a discussion deteriorates into an exchange of insults, hyperbole tends to displace facts. When people become emotional, they become more prone to fallacies which appeal to emotion. In most persistent disputes, each side may have some facts to support its position, but with anger comes a hardening of positions and a refusal to consider the other side's case. People may lose sight of the actual disagreement, and instead focus on trying to harm the opponent, creating a cycle of vendetta. Don't let Wikipedia sink into the online equivalent of the conflicts that wracked Belfast, Baghdad, and Beirut at their worst. Cultivate sangfroid instead.
Departure from rules
Wikipedia maintains remarkable coherence despite the vast diversity of its 37,802,933 registered users (and a comparable number of unregistereds). Wikipedia is able to do this by defining a comprehensive set of policies and guidelines that tell editors what to do in most situations. When disagreements occur, the cause is either that one or more editors are not aware of the applicable rules; different editors interpret the same rule in different ways; or a new situation has come up and the rules do not cover it yet.
The best way to avoid or defuse conflict on Wikipedia is to know the rules as thoroughly as you can. Not just individual policies and guidelines in isolation, but how they fit together and the underlying reasons for them. Then, in most cases, disputes are easy to resolve by simply pointing to the applicable rules. This helps to take the focus away from individuals and their emotions of pride and self-worth, and instead make it about reading and following instructions. As long as everyone on Wikipedia agrees to do the latter, there is usually not much to argue about.
When disputes get out of hand, and administrators intervene, they generally favor the side which most closely follows the rules. But when a dispute arises and the rules don't cover it, or when a rule needs updating, editors should work carefully to reach consensus. The resolution affects not only the current dispute, but any number of other editors may rely on the findings when similar situations come in the future. Resolving a conflict therefore adds value to the entire project. Many features of Wikipedia that we take for granted arose from past disputes, some of them bitter. We are able to edit productively because we don't all have to keep fighting the same battles.
When two sides devolve into calling each other names, they are not getting closer to finding the consensus which could add another important piece to Wikipedia's structure of rules.