Many years ago, I cut off another driver to get into a car wash 1st. Felt a little crappy, but I got in there. Walking along, watching my car, the other driver moved up beside me. Well dressed business type; he looked at me and quietly said, "you've got bad manners." I knew, I knew, but it really rubbed salt in it and I never forgot.
Just a few years ago, I was pulling out of a business driveway in my pickup/camper, ready to turn right and with the turn signal on. A lady pulled up on my right side, then zoomed into traffic ahead of me...and it burned my butt. She pulled into a convenience store just down the street and, by chance, I was going to the same place.
I got out ahead of her and held the door of the store for her. She wouldn't meet my eyes. I said, quietly, "you've got bad manners." You should have seen the flusterpation. "abadyabady"....red face and all. Haha....it felt good.....and this is a true story.
I completely agree with the OP.