This seems to me like a very High School English teacher inspired interpretation of the story. I'm not sure what your distinction is between opinion and thesis,

This seems to me like a very High School English teacher inspired interpretation of the story. I'm not sure what your distinction is between opinion and thesis, but in either case the "sins of the father" quote is just a dramatic element of the story. The thesis IMO is quite clearly a critique on the hypocrisies of the Norwegian society at the time. The characters in the book that all proclaim traditional values and virtues are all hiding despicable behavior while the mother and son subscribe to a more progressive morality and are punished for it. Also Carver might feel more vital and reel considering his stories are about people in my parents or grandparents generation (people I've met), whereas Ibsen was writing when Victorian England was still a thing. I love both authors btw.