The really nasty stuff (the stuff featured in the BBC doc trailers) often only occurs after a driver is challenged by a cyclist for a dangerous bit of driving, close overtake, on phone etc, especially if you give the car a knock, this sends people crazy.
Is it completely counter-productive to challenge drivers? I've done it and most of the time it results in aggression from the driver (half shouted road tax / get left argument while the lights are changing) or just a complete ignore/shrug shoulders (mainly bus drivers). Only twice have I had an apology and a few times I've had a guy get out of his car and start with the physical threats (I rode off and made a turn that they weren't making)
I believe it's the helplessness + the adrenaline from the dangerous situation that makes us challenge, i've started down the ultra polite, calm down, smile "excuse me, sorry to bother you, would mind awfully just giving me a little more room, thanks" line which is pretty hard when your heart is thumping and it's 2 degree's C and your mouth is frozen.
The 'war' in the BBC documentary is the camera footage of small people reacting to being challenged for there own poor behaviour, people believe they are untouchable in their cars