A person judges others because of their low self-worth and lack of self-esteem. They are judgmental because of their own constant self-criticism as well as their generally negative outlook.
It is a process in which the more a person may feel bad about himself, the more likely he is to condemn others to increase his ego.
However sometimes people have a false opinion about themselves and they feel that they are superior to others in terms of their looks, skills, knowledge etc. This false opinion makes them fall in the eyes of other people.
Such people cannot build a bridge by meeting every single person. Building a relationship takes time and effort.