"Judge not, that ye be not judged" (Matthew 7:1).
This is a very familiar maxim, often cited by unbelievers and carnal Christians as a rebuke to Christians whom they regard as intolerant. These words of the Lord Jesus Christ do, indeed, warn us against a self-righteous attitude, condemning others who disagree with us on the basis of superficial criteria.
On the other hand, this caution by no means relieves us of the responsibility of evaluating the beliefs and practices of others in the light of Scripture. In the very same sermon, in fact, Jesus said just a few moments later: "Give not that which is holy unto the dogs, neither cast ye your pearls before swine"; and, "Beware of false prophets, which come to you in sheep's clothing" (Matthew 7:6,15). Obedience to such commandments obviously requires one to make a judgment as to whether certain unbelievers should be regarded as "dogs" or "swine," to whom it would be counter-productive to try to speak of spiritual matters; or whether certain professing Christian leaders are actually false prophets who should be repudiated. Jesus also said: "Judge not according to the appearance, but judge righteous judgment" (John 7:24).
Since the Scriptures themselves are to be used in the final judgment (John 12:48; Revelation 20:12; etc.), it is obvious that we should use them right now to discern truth and error, right and wrong. "For the word of God . . . is a discerner of the thoughts and intents of the heart" (Hebrews 4:12).