"You're doing it wrong."
Inevitably, we will run into someone who is doing it wrong. An idiot. A moron. A retard. Being perfectly objective, rational, intelligent people, we will point out their many flaws. Since they are irrational, they will argue. What idiots!
Let me introduce you to MAWT: Mutually Assured Waste of Time
When you start a conflict, be sure that whatever is lost due to the conflict is more than offset by what is gained by winning. While the other person may be an irrational idiot, starting an overly expensive conflict just to make them do it right is just as irrational. Sinking to their level fixes nothing.
This is merely looking at one incident. If the conflict instead addresses a pattern, a habit, a persistent social problem, then the benefits are greater, though not always apparent. In that case, the conflict may be worth it in the long run. However this calls for a different approach. To solve a long-term problem, one cannot focus on short term gains. As satisfying as it is to call someone a retard, it triggers defensive reactions.
Are they retarded? By the dictionary, probably not. By common usage, perhaps. But if you are not changing their behavior, are you really any more intelligent? The retard in question may even repeat the negative behavior out of spite. Irrational, but if you triggered that irrationality, are you much better? Before your intervention they did it mindlessly, rather than intentionally, and didn't have much incentive to continue or not.
Retards are very good at being retarded, don't try to beat them at their own game. It's retarded.
P.S. I realize I used the word retard much more than I would normally. That is for contextual reasons.