Serpent Of The Evil River / The Transplant - S2-E9
Trivia: When the computer is telling Courage about the giant kangaroo monster, the chicken it steps on looks just like the alien chicken from the very first episode of the show. It even has red eyes.
Answer: Eustace is a rather two-dimensional antagonist character. He is just a mean-spirited man who takes out his hostilities on a vulnerable dog and resents his wife having adopted him.
raywest ★
I thought the reason had to do with the attention Courage receives from Muriel.