I’ll toss in my experience from today - 3 lane highway I come up on a car in the far left lane a truck in the far right lane and a half mile of nothing in the middle lane. As I’m sitting behind this car and waiting for them to merge over to the middle lane I realize that they’re being a road hog and I will need to pass on the right. I complete the pass and return to the left lane and this person decides that my passing her somehow earned me the 1 finger salute out the window. Had I been tailgating or cut her off when returning to the left lane I could understand but I gave plenty of space and the act of passing was apparently too much of a blow to her ego.
Also saw this posted on reddit yesterday and made me laugh: