One could argue that some of the cycling related violence is done for fun and nothing else. People I know have had bottles chucked at them in some "bad" areas. One person I know almost had a metal folding chair chucked at him in a bad area for "fun." The point being not that this is cycling related issue, but there is a strong American cultural proclivity to engage in violence for fun. We do have to watch out for that, as cyclists are an easy target. The only thing which made this unique was that these people would have taken out a car driver for fun. That is less common.