Grandpa fought in the ETO (he was particularly glad when Truman dropped the big one, as he was slated to go to Japan, next). Still hated the Japanese. When his daughter (my aunt) came to visit driving her new Mitsubishi, he suggested that she park the car around the back, behind the house, where no one would see it.
He was only joking, but not really.
AFAIC, there's nothing wrong with a good grudge. People forgive and forget too easily, nowadays.