Your argument is based on this premise, ..."This seems to show that the negative emotion of anger is far more common in chess than people want to admit..."
I am, however, quite sure that many of those just lose interest in a game that they are losing.
I agree with you that it's not a good way to play chess and those people should either play the game fully or resign.
Just saying....
Playing against better players does not help one improves. Unless you analyze the games you lost and discover the mistakes. Without discovering the mistakes, the same mistakes will be repeated again and again.
Seems to be working for me.
Playing against people who punish your mistakes is bound to improve your chess. Playing against people who don't punish your mistakes (weaker players) will not make you better as a player. Often times you can beat a weaker player even if you play far below your own playing level.