Wherever you go, there would be always some troublemakers that would harass you no matter how you treat them. But, that don't give you the right to fight back as there are police that would take care of them. Just report those bad guys and the cops would take care of them. This also applies to vehicles.
The game is played via mouse and the idea here is to fulfill each requirement. Each level has different requirement. Most of the time, you would need to park your vehicle, but there are times that you need to push law breaking vehicles.