How to Get Lawfully Pew-pew'd: Smash Into Occupied Car

A motorcyclists riding amidst a crowd of others in Philadelphia got angry enough with a car driver that he decided to jump on the car's rear window and smash it into the vehicle. Would the occupants of that car have been legally justified in simply shooting that motorcyclists dead? What if that same motorcyclists had a pistol in hand when the car driver exited the vehicle to confront the rider? THERE IS ONLY ONE SELF-DEFENSE INSURANCE PROVIDE I TRUST! There are lots of self-defense ...