It demonstrates the emotional context of using the “N” word in a society of that time, the imposed attitude of the right interpretation of the “N” word by the conditions in which people used to live.
The situation with Scout’s conflict shows the real power of discrimination, which instills the proper reactions on actual movements. People forget that they have a choice to form their own points of view on the established opinions and reactions. It was a huge problem to question the traditions and conditions of people stratifications.
Why was Scout moved to anger without even knowing the core of a problem? Because she knows the right identifications of the “N” word and she didn’t even think about the chance of positive interpretation. It was clear and obvious.