There are many threads regarding confronting bad cyclists (red light runners, stop sign runners, riding on the sidewalk). Most suggestions are not to make the confrontation but if the offense is really bad and repetitive report it to the police. Offending motorists will be worse. It's not worth your aggravation and time.

I've once had an impatient driver pass me only to lose control and almost get into a collision with another motorist heading in the opposite direction.