In Buddhism, must we be completely non-judgmental? Let's say a person has an explosive temper, and he knows it's bad for his health, bad for people around him, and so on. Only if he condemns it, he'll be able to change it. If he adopts a non-judgmental attitude, would he have the desire to change?
So I am wondering what we must do when confronted with anger, lust etc.. If we judge, we have a problem. If we do not judge, we have a problem. What must be done?
This is a good question and a fine point that is often misunderstood in Buddhism. "Non-judgmental" is the term that has become popular in English to mean "equanimity." Having equanimity with anger does not mean that one doesn't act to change their behavior. In fact mindfulness and equanimity are a viable alternative to acting on aggression. When the anger arises, one watches the thoughts and emotions as they arise, change, and pass. One allows these to come and go unimpeded, without judging or condemning them, but also not feeding into them, treating them as reality or self. Instead they are observed as passing events, e.g. "Anger is occurring," instead of "I am angry."
A person reflects on the anger, seeing whether feeding into it is skillful, whether it would cause benefit or harm to oneself and others. Whatever one dwells on becomes the inclination of the mind. So not only is it harmful now, it eventually reinforces the habit. If a person is preoccupied rejecting and condemns oneself and/or these internal experiences, one doesn't get to watch closely and observe the harmful effects. In observing these harmful effects, one can make a compassionate decision, compassionate for oneself and others, to think and act differently, to find more skillful alternatives.
The non-judgmental attitude, equanimity, is with the internal experience one has. One can do that and still make appropriate to make changes in behavior. Judgment, in the sense of moralistic condemnation, is beside the point.
Also see Gil Fronsdal's "Working With Anger" on p. 72:http://www.insightmeditationcenter.org/documents/iah/IssueAtHand4thEd.pdf