No overreaction here, I would have done exactly as you did perhaps even taking it a step further. To tell someone that film still exist is of course a nice gesture but would not have change this persons persistence to take his or hers tripod legs into the same spot as yours before you could get out of there.
I have had the same experience as you did, did not take a shot as it was not worth a sheet of film but the over ambitious photographer kept pushing to get me out of there so he could set up his camera.

It is lack of respect from the other person that made you react as you did and your reaction is fine as far as I am concerned.