People act upon impression which does not indicate fact and so people are incorrectly judged and labeled.

we HAVE to judge. if we never judge anything or anyone, based on our past experience or other learning, every step we take will be tentative, finding out anew each time whether the floor will support us. the trick is not to refrain from judging. the trick is keeping an open enough mind to let new information in even if it conflicts with the initial judgment.

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Because people take a number of conceptual shortcuts in order to function quickly in the world and one of the big ones is snap judgments. Natural selection has bestowed this tendency upon us because it is a survival advantage (note, I did not say it was a thriving or enjoyment or happiness advantage, because natural selection does not "care" about such things). If you can quickly assess whether a stranger is a threat vector then you can decide whether to trust or run, etc. People who hesitate might get killed. This is literally the subjective internal calculus.

Happily, snap judgments and other forms of confirmation bias can be worked on and tamed. Unhappily, most people have no training in critical thinking and little accurate / nuanced understanding of human psychology, and so don't usually bother. Best you can do is understand it yourself, so when you see it in others you don't take it personally.

It's easier to judge others than to actually listen to them, requires less mental capacity. Same goes for hypocrisy. Thinking through your thoughts and trying to be consistent is harder. That's why fighting religions is an uphill battle.