Indeed, we must judge, but not in the way you indicate. An ancient communion prayer, still said in the Orthodox church by priest and congregation together, begins "I believe and confess, Lord, that You are truly the Christ, the Son of the living God, who came into the world to save sinners, of whom I am the first"  (or chief, in some translations).  

In other words, the prayer reminds us to judge ourselves in the presence of the mercy and self-giving of Jesus, but that judgments of the spiritual state of the souls of others are not for us to make, but up to them with God. Not to say that we cannot judge the effects of their actions on people harmed by them  - that's an entirely different matter.