See I think sometimes people just give others more credit than they deserve.
For all you know the guy just couldnt drive for sh*t and was trying to keep up and bashed you...then you look like the complete ass for blowing the mission for some nub.
Maybe the people running others over arent on purpose. Maybe people get left behind because others dont pay attention and didnt see you had no car. Maybe someone is new to a mission and didnt realize it was not an NPC in the helicopter.
An example would be myself. I am a lvl 275 with a second character at lvl100 and I would not have the slightest clue what is going on in these missions as I could count on my fingers how many of them I have done.
Things are not always as they seem.
The first time the guy tried to ram me he said "Take this" over the mic, The next time he rammed into me he said "Got Ya" I see where you're coming from (Some people really do suck at driving) but this guy did it on purpose.