I just think people are pricks. I had one on the M1 - coming out a 50 mph zone, traffic all bunched, flashes headlights, right on the bumper, for a mile or so. Eventually when safe I just move over, but with the middle finger scratching my nose gesture. I get the full on window down wanker treatment from the passenger who then decides to try and spit. Not a great idea at 70 mph mate. Said car unsurprisingly then sits behind the queue of traffic, then decides to weave for a few miles.
A day for it, heading down Burncross Road post game, 3 lads on mountain bikes just weaving about the road, one on the wrong side. Just suggested the prick get off the road, the only pity was the discussion was brief as a further 5 seconds the car travelling up the road would have nailed him.
I probably get more annoyed that I react to these arsewipes