This his very true. Here is a real example of what could happen:

http://www.wbir.com/news/local/story...storyid=224522

short version:

motorist does not give cyclist enough room in construction zone
cyclist reaches and touches motorist's car to maintain balance
motorist becomes enraged
cyclist stops on the side of the road to catch his breath and recover from nearly being sideswiped and taken out by motorist
motorist returns to attack and punch cyclist
cyclist in hospital with fractured cheek and eye socket