So someone has an accident, which you didn't see at all, and your first reaction is to stop, hurl abuse at the person when he is quite clearly shocked and traumatised after the event which most people would find pretty scary, and then you post here as if we're supposed to pat you on the back for being a shining example of an alpha keyboard cowboy? Quite honestly, you're what's wrong with the world today. No facts on the matter, just straight in there with the blame culture. Good one. I suppose if he'd have hit you or something then you'd be straight in there pressing charges despite you antagonising him.
It's not uncommon for people to get angry towards someone after they have put them at great risk. If the op had kids in the back of his car I'm sure prolonged verbal abuse would have followed.
I suppose the correct thing to do in this situation is pull over, make sure the driver is ok, and if the damage is bad then call the police to say there is bits of car all over the road. But having a car almost swipe in to the side of you makes your brain go off in all sorts of directions.