Freewheeler has a link to an article describing a cyclist being attacked in Ealing by three men, after having the temerity to be knocked down by them whilst they jumped a red light. From the report it appears they also intimidated some witnesses on a bus. Absolute charmers, I am sure.
The Cycling Silk describes on his blog an incident with a motorist and another cyclist, where the car driver got out of his car and confronted the cyclist, and then proceeded, for no apparent reason, to knock off the cycling silk from his bicycle as he waited to turn right. He was knocked into the path of incoming traffic. The driver got a caution.
It probably is worth saying that actual threats and assault isn't a common occurrence when cycling. Most of my issues are because motorists are impatient, or inattentive, or just don't understand what to do around cyclists. Some attempt bullying (edging out, use of the horn), but nearly all of this is simply impatience which is cured by an assertive look.
But it is clear these attacks happen. And when they do, it appears that the police and CPS don't take into account the huge disparity between a cyclist and someone piloting a tonne or more of metal. These incidents should be taken seriously with motorists knowing that there are consequences for anti-social behaviour. In both instances, the fact the victim was a cyclist is immaterial - I suspect the same aggressive behaviour would have happened if the victim was driving a car. But the instigators of this aggression need some serious consequences to jolt them out of this behaviour. Maybe someone who cannot control their temper to the point they assault someone or use their car as a weapon should be relieved of their license until they can prove themselves fit to drive?