We do stupid things when with other humans, particularly our peers. The mob mentality comes about as people lose their identity and find support for their baser emotions. The anonymity of a mob allows for people to act without fear of reprisal, while the mirrored support makes the members of the mob feel more justified in their beliefs and actions. Social media has heightened that.
More than once I have written about the dangers of the echo chambers that social media accounts provide. The algorithms based on your search preferences, time spent, and responses "feed" you the information that is most likely to provoke a response from you or to make you spend more time looking at the screen. This leads people to believe that they have sided (whatever side they have taken) with a majority view, validating their own beliefs.
Meanwhile, even with our names attached, social media allows us to easily get into arguments with strangers. Although their names are provided (and sometimes their profiles), these unknown people are too easily dehumanized in our eyes, leading us to speak to them in ways that would not were we to meet them face to face (at least, hopefully we would not). This dehumanization also allows us to associate their beliefs as being less than human, and since they are often dealing with the same issue, their lack of respectful language only heightens our certainty that they are clearly in the wrong.
These are dangerous trends. No wonder people are so surprised (on both sides) to find that this Presidential election is so close. People from both of the two major parties are certain that they are going to win by a landslide (or a tsunami?) because of the confirmation bias that they have built from the information that was custom-provided for them. Instead of dialogue, ultimatums and insults have been the primary method of communication between them ... and all sides feel justified in doing this because of how the other sides have presented themselves.
I don't know how to solve this. It involves way more people than Scout's situation. I doubt that bringing up the difficulties of a person's entailment will be enough. Still, I think that humanizing those with whom we disagree might be a good start.