One time I was walking along the pavement while singing (weird I know but there was no-one about...) and momentarily glanced at a driver who pulled up, got out of his mercedes and started screaming at me 'EXCUSE ME, EXCUSE ME SIR!."
I ignored him, didn't look back and eventually his wife and children started shouting at him for making a fool out of himself.
There are some serious nutters in this world, not just on the roads but everywhere, who do not take much to set off. Best advice I can give is to focus on your positioning and awareness when cycling and treat drivers (and other cyclists) as part of their machines rather than people with personalities.
While cycling your priorities should be to anticipate other road users doing unpredictable things, positioning yourself to try to prevent them doing unpredictable things, and to remove yourself from danger if they do attempt said unpredictable things. No point getting wound up if someone does something stupid but ultimately hasn't harmed you as you are more likely to get distracted from anticipating other road users doing unpredictable things. After all cycling is about getting from A to B safely in good time or just for pleasure, no need to let some argumentative motorist slow you down, compromise your safety or spoil your mood.
I know some people here say drivers need to be educated, and there are probably some who do benefit from being told their driving is poor. However there are some who are willing to get out and threaten you with violence and the thing is you can never tell what you are going to get if you provoke them. If someone does get out and approach you then you need to make sure you are willing to take them on or plan an escape route because you never know when it might get nasty. In my opinion it is just not worth it, just cycle on and pretend it didn't happen, be more zen or something...