I think that the cyclist was attacked after challenging the driver, not for complaining. Granted the driver was chasing him down and harassing him by repeatedly blocking the cyclist but that's not the attack. He was making a point, similar to the "car always wins" point above.

My motto is "Don't engage the crazies". That works regardless of whether you can beat him in a fight, or in a court, or on the road. Once identified, don't engage.