So I agree unless you are sure of where you are at, stay in the car and let it go.
My friend (a fiesty Cleveland gal) flipped another woman off in San Francisco (Market Street) at the next light the woman got out of teh car and walked up to my friend and pulled a gun out and held it to her head and then yelled at her. Something about how it was impolite to flip people off.
Then she turned around and left.
My friend doesn't flipped people off anymore.