Recently while driving on a crowded California freeway, where traffic had frequently come to a complete stop, I felt happy to see it pick up. My lane was still slow, so after letting a motorcycle pass on the left, I signaled and moved over.
That apparently irritated the motorcycle coming next, even though I judged him to be far enough behind to allow me a safe lane change. He pulled up next to me, as close as he could get, and screamed unknown things. Next he started hitting my car, apparently trying to break my side mirror. He succeeded in turning it around and then drove off.
Thing is, had I moved ever so slightly to the right, he'd be dead. The road was still crowded and at best he would likely have been run over. So I saved the life of this guy who was raging at me. I doubt he was grateful! (And I am glad he didn't seem to have a gun!)