We all misperceive what is in front of our eyes, ears, smell, touch, because we perceive through our filter and lens of experience which skews our perceptions in expected and prejudiced directions. We perceive through the lens of what psychologists have called the "self fulfilling prophecy".
Is the glass half full or half empty? Is that event a blessing or a curse, a good thing or a bad thing? History usually gets written by the victors, the oppressors, the more dominant people in the relationship.
So the wise person is not judgemental because (s)he knows that judgement is flawed, imprecise, skewing interpretation and meaning in an prejudicial direction. The wise person knows that only God, Spirit, Mother Nature, Tao can take the ever flowing, changing, oneness of life into account.
The wise person is aware of the seventh principle/value of Unitarian Universalism - "Respect for the interdependent web of all existence of which we are a part." The meaning we make of our existence very much depends on our perspective, on our limited experience. Recognizing our ignorance we are moved to humility and we become nonjudgmental.
As Jesus said, "Judge not so that you will not be judged." Matthew 7:1