the.com/tribalism

means Strong loyalty to one's own group, often strong enough to override fairness, facts, or judgment toward outsiders.

from Built from 'tribe' — Latin 'tribus,' originally one of the three divisions of the early Roman people, later used for any people, clan, or ethnic group — plus the '-ism' suffix marking a belief system or pattern of behavior. The word itself has drifted: once a neutral term for how traditional societies organize, it's now mostly used to describe the modern, often political, habit of circling the wagons around 'us' against 'them.'