I know there have been fights between runners, and bad feelings when someone cuts too close in front during a race, etc., but it's extremely rare, considering the huge numbers of runners. You see baseball fights, hockey fights, fights in football, angry words back and forth in tennis, you name the sport. I think it's because "our sport" is so basic to our evolution. The ability to run meant life or death to whole civilizations for literally hundreds of thousands of years. It is something that rests deep within ALL of us at some level. It was the sole means of traveling, getting food, and escaping predation until a few thousand years ago. That is why, even when it hurts, it leaves us feeling good.
As I have said in previous posts, if you run, you are a runner. That's all it takes. You may be a "fast runner", a "slow runner", a sprinter, a distance runner, etc. Those are just adjectives. Stick with the noun. You are a "runner". Go run.