Question: When Lisa guesses that Mr. Bergstrom is either Jewish or Italian, why does he quickly say that he is Jewish? As if he certainly doesn't want to be mistaken for Italian?
Answer: When I was a child, my classmate said I could be Jewish, Italian, or Middle Eastern, but I couldn't be what I truly was, Mexican.
Answer: Because Lisa thinks that her feelings are so intense and special that no one else could possibly feel the same. A lot of people act this way when they first fall in love (insisting that no one else has felt this much in love). Lisa also knows that Homer is far from the perfect husband.
Gary O'Reilly