A physician, an ER doc if the story is accurate, caught another rider on the way up the long climb. The doctor noted that the guy he was catching was not wearing a helmet, and (having seen lots of cyclists with head injuries) suggested to the fellow that he might think about wearing one.
The guy hit the doctor in the face, knocking him off his bike. The slugger kept pedaling, feeling (we suppose) that justice had been done.
Here, from Madison WI, is more evidence that mere suggestion is, in the minds of some, sufficient provocation for violence: http://www.wkowtv.com/Global/story.asp?S=9453608