This scenario is one example of the Signal Detection Theory. It can be that Marge is interested with the topic of the upcoming election that is why she was able to pick up the conversation despite the background noise in the restaurant. This is also why Xavier was not able to hear that conversation.
The answer is: Prejudice
Prejudice is a form of perception that we have toward a certain group of people without being backed by facts or actual experience.
Prejudice is often formed from generalization. For example, when we constantly see in news and television only reported the crime that conducted by a certain racial group, we would most likely grow up believing that members of that racial group is more prone to do criminal actions.
Slavery in the Chesapeake region began in 1619, when a Dutch trading vessel carrying 20 African men entered Jamestown, Virginia. The slave trade expanded in the following years. Between 1700 and 1770, the region's slave population grew from 13,000 to 250,000. By the beginning of the Revolutionary War in 1775, Black people made up nearly one-third of the region's population.
In the 1800s, the Chesapeake region became a focal point of the national controversy surrounding slavery because it was in the unique position of spanning free, border and slave states:
“Free states,” which did not support slavery, made up the northern portion of the region.
“Slave states” encompassed the southern portion of the region.
“Border states” allowed slavery but were allied with the free states, further complicated the region's politics.
