Judging people is a common habit of ours. In certain circumstances, when we have enough information this may not be entirely wrong. But what is absolutely wrong is to judge people by our own standards. We must judge people by their standards. If a person is conforming to his own standards, it means that he is a sincere and a truthful person even if he at times falters. We may differ with his standards but this is a very minor point in this given context.
When we judge people by our standards we are being self-righteous and egotistic. Whether we like it or not, this is downright injustice to the person we are judging. Two people can behave differently and have different standards. If we do not concede this, we in fact believe that people cannot think or behave differently and that they must reach the same truth come what may.
This is not how God has made us.
Judging the people from their appearance is equally wrong as well. If we think that bearded men and hijabi women are always more pious than non-bearded and non-hijabi women, then we are sadly mistaken. Appearance at times can be misleading. We cannot know how a person is from his or her inside. It is only God who has this information. So, why take up the work of God.
And if we are very fond of judging people let us judge our own selves instead of judging others!