I would be the first to say that we are not here to be judges against sinners, but rather to bring salvation to them and bring them into the freedom from sin that Jesus offers.  We are to be what he was, which is an example of holiness and righteousness rather than judges of their sin. .

When it comes to sin we would be much better off looking within ourselves in order to purge ourselves of all sin before we go out looking at the sin of others.  Jesus taught this directly by his parabolic example of those more concerned with taking out the splinter (mote) from their brother’s eye rather than removing the log (beam) from their own.  However, we must take this advice in the greater context which includes his attitude towards the hypocrite and false prophet.  Although he does warn us against judgmentalism he also warns us not to bring his holy word to those who are so depraved of truth that they will turn on us to destroy us as found in verse 6.  So in order to determine just who these people are who are depraved of truth we must make a judgement.  So Jesus is not only permitting us to judge such people, he is commanding us to do so for our own safety.

The problem I see here is that many people tend to stop reading after verse 4 where Jesus warns against judgmentalism and they never get to verse 15 where Jesus tells us to beware of false prophets. When he tells us to beware and judge their fruits he is telling us that we must make a judgement as to their truthfulness, sincerity, and holiness. In verse 17 he even refers to them as corrupt.  Determining if someone is truthful, sincere, holy or corrupt is a judgment—is it not?

So to summarize Jesus’ teachings on judgement we have to say that, first of all, we are not here to be judgmental of others simply because they don’t agree with us. Neither are we here to judge the sins of the world—for that would be a never-ending job that would take us away from our true mission of bringing salvation—besides true conversion can only come when they feel the judgment of God not ours.

We are here to judge what is holy and righteous from what is evil and sinful mostly for our protection and the protection of our faith. Our judgment is to be made against those who say they believe, but continue to live in sin.  Their rejection of all judgment of sin challenges the existence of sin itself for by denying sin they justify their own practice of it while still claiming to be Christians. Such people fall in the category of being false prophets and hypocrites and must be called out for being such. 

We cannot become absorbed in the sins of others for then we become distracted from our true mission to the world of sinners which is to be models and examples of holiness for the purpose of bringing them to the Lord.

Our judgment must not be based upon our desire to make ourselves look righteous for this is self-righteousness, but must be to preserve the holiness and righteousness of Christ as he manifests these through the believers of the church.