The problem with ethnocentricity: "ethnocentrism as often leading to pride, vanity, the belief in one's own group's superiority, and contempt for outsiders.

by American sociologist William G. Sumner.^[4] In his 1906 book, Folkways, Sumner describes ethnocentrism as "the technical name for the view of things in which one's own group is the center of everything, and all others are scaled and rated with reference to it." He further characterized ethnocentrism as often leading to pride, vanity, the belief in one's own group's superiority, and contempt for outsiders.^[5] 

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https://en.wikipedia.org/wiki/Ethnocentrism

Ethnocentrism - Wikipedia

This is the main problem of ethnocentricity. People on the far right  and far left, for example, contempt for those on the other side. But then, one of the problems is that people on the far right are more likely to be armed. And people on the far left will exact revenge in more educated ways upon their perceived enemies.

And in the U.S. there is a perpetual hopefully non-violent war between these two extremes. However, in Covid times because of increased stresses caused by the pandemics it is much more likely that violence between the far right and the far left will occur at different and unexpected points.