Why are people idiots,and what to do when this happens?

my brother and me went to the speedway near our house and the intersection was full of cars, there was an ambulance coming from the south facing road, it had to move to the wrong side of the road to get through and turn right towards the highway and some other places. when the ambulance was about to turn some retard in a blue car turned into the ambulances path and they both had to stop. then the ambulance got out and continued on its way. my question is what exactly are you supposed to do when this stuff happens, i have heard that you are either supposed to turn the corner and stop(for non crowded roads and when its behind you) or dont move at all(unlike the retard above) i was laughing at how retarded the guy was for almost crashing into the ambulance.