People who compound a rude action with a rude reaction to it.
I was in a movie theatre yesterday, sitting in the aisle seat of the second row from the middle (the row just behind the one facing the divide) with a large cup of coffee in the cup holder end of the armrest. We were there for the opera broadcast, which was to start in about an hour.
Of course, having the aisle seat in that situation means having to pull in or stand to allow others to pass, which wouldn't have been a big deal if the same people didn't make multiple trips in the space of 20 minutes. One couple did this and the man knocked over my coffee cup, which was still 2/3rds full. No warning, and the cup landed under the seat in front of me, which was then occupied. I looked up in time for the landing and said, "Oh, no; there goes my coffee!"
The transgressor said "That's why God invented restaurants."