Never attribute to malice that which is adequately explained by stupidity.

We go 'round and 'round on this all the time. Why would you confront someone like that so aggressively? What if he'd pulled a gun when you were at the light yelling at him? Would you feel you handled it well then? @Number400: if the driver had gotten out with a weapon, instead of driving away, where would your antics have gotten you?

Smile, wave, take the license, call the local LEOs. Confrontation between a 50-pound bike and a 3-ton car or between you and a stranger of unknown stability is dangerous.