Bikeboy, see if you can wrap your head around this idea: Knowing You Are Right = Narcissism. It is not a case of one or the other, as they are the same.
One of the 10 Cognitive Distortions is "Black-and-White Thinking". The concept of 'Right' and 'Wrong' is one aspect of this primitive type of thinking. Humans have evolved in a way that has enabled them to think in "Shades of Gray", and that ability is primarily due to a larger pre-frontal cortex that allows expanded reasoning skills to develop. Those with Cluster B PDs, which include NPD, have difficulty in maintaining adequate activity in their PFCs. Stimulants, both chemical and physiological, promote better PFC functioning for those individuals.
So basically you are self-medicating when your PFC has trouble receiving and processing a external input that is contradictory to your current way of thinking. The problem is, the raging is a maladaptive means of PFC stimulation, and it hurts your close relationships since others (Nons) do not need that kind of stimulation and grow resentful of your boorish behavior.
The better means of dealing with such occurrences is to accept that there is no 'Right' and 'Wrong', and to train yourself (probably with assistance from a therapist through CBT) how to alter your Black-and-White Thinking into Shades of Gray Thinking. It will lessen the importance you place on trivial issues (e.g., everyday annoyances) and help you to view the others' perspectives, even if you cannot directly relate to them (because of lowered empathy, another PFC-based problem for NPDers).