I have calmly asked a chap to pull over and then explained why I had an issue with his driving- all very non-confrontational.
He pulled his van over onto the median and we had a chat.
I (in the spirit of extreme yoghurt weaving) suggested that he try a cycle training session to see the world from the other side of the steering wheel, which I would arrange and pay for.
His response was that he didn't see why he should do that, and he'd do the same thing again- and if he killed someone "well I'd just do the time".
So- my conclusion is reason is wasted, if the person has behaved badly enough to endanger you or yours then suck it up, or pull them out of the car and express your displeasure physically.
Were you dressed like this at the time though?
http://www.lfgss.com/thread110020-3.html#post3708586