This is an interesting post. I am not a runner but I was a college baseball player and I knew what it meant to work your tail off, practice long hours, and sacrifice a great deal. What I find with avid runners and I have known a great deal of runners either recreational or semi-serious half and full marathoners, is that they do begin to develop a rather self absorbed and almost sensitivity about their running. There is this misconception in the running community that what they do is not considered a true sport by other athletes. Where this came from I have no idea because I'm not a runner. It's a stigma that is look down upon very strongly by those in some running circles and they almost perpetuate other runners to take this very confident, self serving attitude towards what they do as a defense mechanism. Runners become very close with other runners, relationships are forged based on common running goals, and I have found that runners after a while become very hard to talk to.
Everything revolves around running, their training, their upcoming races, their workouts, their taper weeks, their nutrition, etc. It became so bad that I could no longer associate with some good friends because they literally turned into running "narcissists". The topic of every discussion eventually turns back to running and related topics that relate most closely to their interests.
I hate to make a comment that seems off color, but I know that a lot of runners I knew were never true sportsman or had any other talent in other sports before they took on running. Now don't take that comment as an insult because it isn't however, I was able to relate to my fellow baseball players and "non-baseball players" and the conversations did not always revolve around baseball! I frankly grow tired and worn down when I am in the company of people who are serious runners. It consumes their every breath and sometimes I feel sorry that they have let running become their only true identity.
Many runners lose themselves and lose the interest of those around them that don't share in their love of running. The opposite is true too, many runners lose interest in others who dont share in their new found hobby.
That being said, I would say that YES, some runners do become very self- centered and narcissistic in their thinking and it's sad that this "hobby" defines them and defines how they interact with other people. It almost makes them isolated in the long run (no pun there).