There are a few reasons this passage might be worth interpreting:
1. This passage demonstrates that even after the trial, Atticus' own sister still has prejudices and hatreds that run deep.
2. It demonstrates that no matter what, there will always be different types of people in the world that are worth value, not that we always give them value. This passage demonstrates the evil of intolerance based on a person's cultural mannerisms. That is not nice, and it's not fair.
3. It demonstrates a difference in Atticus' and Alexandra's values. Alexandra values family because they are related. She has pride in her family. Atticus accepts his family scars and all, which demonstrates that he understands humanity, we all have strengths and weaknesses.