You are both right:1) He *can* legally photograph from outside the vehicle, anything which he can see through the windows, the same way he can legally look at anything visible through the windows. But he can't lean into or enter your vehicle--that is trespassing.2) However, even if he trespassed, you cannot push him away--that can be assault or battery, since the law does not give you a privilege to use force, even minimal force, on someone who is not a threat. The legally correct response would have been to call the police on him--preferably after using your cell phone camera to photograph him trespassing, etc.