There are two schools of thought with regard to this sort of behaviour and this includes, rubbish out of the window, accidentally or deliberately cutting you up, moving over to prevent filtering, pulling out in front of you at roundabouts, I'm sure you get the picture, generally shit driving.
1. Put it out of your mind, because whilst their behaviour chews you up inside, you are not concentrating on riding and the consequences are obvious. You come off worst
2. They must never, ever be allowed to get away with it. This is because if they know what they have done, they've got away with it and in their mind their behaviour is acceptable. Or if they don't know what they have done, they need to be told. Either way, they need to be re-educated
I firmly stand in the latter camp, having shouted, cursed, kicked off door mirrors and generally behaved in a bolshie manner. Hopefully, it could save someone in the future, plus it makes you feel better.