I get pretty angry, ala "road rage' when I ride and motorists do something really stupid. Cut me off, run red lights/stop signs, yell at me out the window, etc.
It usually gets me to sprint real fast trying to catch up with them, get winded a few minutes later, and realize it all doesn't matter in the grand scheme of things. But if I do catch them at a red light, I will speak to them.
I don't pick fights with people on crowded trails though. Mainly because I don't like riding on paths & trails. I like city streets.