+1 bazr33.
the key is to stay calm, and give no reaction.
but when it gets really serious there is little option left.
considering that the driver may follow, abuse, and recklessly endanger your/passenger lives.
it would be far safer to TAKE HIM out before it escalates. call it a 'citizens arrest'
or if he is HUGE. explain what just happened, get both sides and figure out who was wrong.
the bloke was probably scared for his family, EVEN THOUGH HE FARKED UP.
and...even if he hits u, its ok=assault, = fine and possible jail time
-hope he uses soap on a rope!