"This strengthened their resolve and encouraged the two groups to hold tighter to their new norms, values, rituals and all other elements if the shared culture."
This demonstrates how at first, the two tribes put together were united and learning about each other which strengthened everything about the uniting of them
" It strengthened their identity to assume the identity of the enemy was a far cry from their own. Everything they learned about the other side became an example of how not to be, and if they did happen to see similarities they tended to be ignored."
Then, despite learning and working together, the minds of the individuals divided the tribes and turned them against each other. They used their knowledge of each other as excuses to dislike each other
This illustrates how people act different around other people because you change according to the power gap between you and that person
"You put on a mask and uniform before leaving for work. You put on another set for school. You have a costume for friends and different persuasions and you have another just for family."
This explain the idea of having "social masks" because you act different while with your mom.
"You quickly change back and tell the person you are with why you appeared so strange for a moment. They understand after all they are also in disguise."
This proves the idea of having "too much" pride and being the all knowledgeable person. The illusion proves to change the way we think based on only how much we know.
"Makes it seem as though you know everyone else far better than they know you, and not only that, but you know them better than they know themselves."
"The illusion of asymmetric insight clouds your ability to see people you disagree with as nuanced and complex. You tend to see your self and the groups you belong to in shades of gray, but others in their groups as solid and defined primary colors lacking nuance of complexity."
This correlates to the quote because it explains how our own minds and our mentality blocks us from seeing things other ways. Our minds automatically divide us into groups and we perceive everything that does not agree with us as negative.