Your autonomous vehicle will call for help, immediately, and the vehicle will be recording all events for investigations, so, the “attackers” will be thinking twice before going after you through your car.
Oh great, it calls for help while I'm beaten to death, because help is minutes away while death occurs in seconds. If the recording survives, it'll show my last words "Why oh why did I choose this car, it's the death of me!". No thanks, I want to control the car in order to save my life.