The desert fathers existed rather early in Church history, and here are a few things they had to say about judging others:
"The old men used to say, “there is nothing worse than passing judgement.”
They said of abba Macarius that he became as it is written a god upon earth,
because just as God protects the world, so abba Macarius would cover the
faults that he saw as though he did not see them, and those which he heard as
though he did not hear them.
Abba Pastor said, “Judge not him who is guilty of fornication, if you are
chaste, or you will break the law like him. For He who said “do not commit
fornication” said also “Do not judge”.”
A brother asked abba Poemen, “If I see my brother sin, is it right to say
nothing about it?” The old man replied, “whenever we cover our brother’s sin,
God will cover ours; whenever we tell people about our brother’s guilt, God
will do the same about ours.”
That’s the first paragraph after the foreword.
coptic.net/articles/sayingsofdesertfathers.txt
Here are some verses from the New Testament that provide some (name removed by moderator)ut about how we are to deal with the problem of flagrant sinners and obstinate dissenters. Don’t shoot the messenger.
Jesus - MT 10:14-15 “Whoever will not receive you or listen to your words—go outside that house or town and shake the dust from your feet. Amen, I say to you, it will be more tolerable for the land of Sodom and Gomorrah on the day of judgment than for that town.”
Jesus - MT 18:15-17 “If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. But if he does not listen, take one or two others along with you, that every word may be confirmed by the evidence of two or three witnesses. If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector.
Jesus - LK 10:10-12 “Whatever town you enter and they do not receive you, go out into the streets and say, ‘The dust of your town that clings to our feet, even that we shake off against you.’ Yet know this: the kingdom of God is at hand. I tell you, it will be more tolerable for Sodom on that day than for that town.”
St. Paul - ROM 16:17-18 I appeal to you, brethren, to take note of those who create dissensions and difficulties, in opposition to the doctrine which you have been taught; avoid them. For such persons do not serve our Lord Christ, but their own appetites, and by fair and flattering words they deceive the hearts of the simple-minded.
St. Paul - 1 COR 5:1-2 It is actually reported that there is immorality among you, and of a kind that is not found even among pagans; for a man is living with his father’s wife. And you are arrogant! Ought you not rather to mourn? Let him who has done this be removed from among you.
St. Paul - 1 COR 5 11-13 But I now write to you not to associate with anyone named a brother, if he is immoral, greedy, an idolater, a slanderer, a drunkard, or a robber, not even to eat with such a person. For why should I be judging outsiders? Is it not your business to judge those within? God will judge those outside. “Purge the evil person from your midst.”
St. Paul - 2 COR 6:14-16 Do not be mismated with unbelievers. For what partnership have righteousness and iniquity? Or what fellowship has light with darkness? What accord has Christ with Be′lial? Or what has a believer in common with an unbeliever? What agreement has the temple of God with idols?
St. Paul - EPH 5:6-8 Let no one deceive you with empty words, for it is because of these things that the wrath of God comes upon the sons of disobedience. Therefore do not associate with them, for once you were darkness, but now you are light in the Lord.
St. Paul - 2 THES 3:14 If anyone does not obey our word as expressed in this letter, take note of this person not to associate with him, that he may be put to shame.
St. Paul - 2 TIM 3:1-5 But understand this: there will be terrifying times in the last days. People will be self-centered and lovers of money, proud, haughty, abusive, disobedient to their parents, ungrateful, irreligious, callous, implacable, slanderous, licentious, brutal, hating what is good, traitors, reckless, conceited, lovers of pleasure rather than lovers of God, as they make a pretense of religion but deny its power. Reject them.
St. Paul - TITUS 3: 10-11 After a first and second warning, break off contact with a heretic, realizing that such a person is perverted and sinful and stands self-condemned.
St. John - 2 JN 9-11 Anyone who is so “progressive” as not to remain in the teaching of the Christ does not have God; whoever remains in the teaching has the Father and the Son. If anyone comes to you and does not bring this doctrine, do not receive him in your house or even greet him; for whoever greets him shares in his evil works.
Not to mention, the entirety of the Epistle of St. Jude and the 2nd Epistle of St. Peter.