Whenever a Christian tells someone what they are doing is wrong or sinful, a non-Christian sometimes would actually quote a Bible verse against the Christian (funny how that works, the nonbeliever quoting scripture against a believer) using Matthew 7:1, "Do not Judge, or you too will be judged" It sounds like a slap in the face back to the believer, telling them "you should not tell me what I am doing wrong" However, if we look at the context, and cross-reference with other scriptures, that is not what the verse is saying.

"Do not judge, or you too will be judged. For in the same way you judge others, you will be judged, and with the measure you use, it will be measured to you. Why do you look at the speck of sawdust in your brother's eye and pay no attention to the plank in your own eye? How can you say to your brother, 'Let me take the speck out of your eye,' when all the time there is a plank in your own eye? You hypocrite, first take the plank out of your own eye, and then you will see clearly to remove the speck from your brother's eye." (Matthew 7:1-5)

So does the context say that Christians should not judge? Read what type of judging we are talking about here. This sermon was pointed towards the hypocrites and those viewing themselves as the judge when they are not. Jesus warns that "the measure you use, it will be measured to you" and saying to hypocrites to "first take the plank out of your own eye, and then you will see clearly to remove the speck from your brother's eye."

Interestingly, as you look at verse 5, Jesus calls them "hypocrite"...Jesus himself is judging the people who are judging hypocritically. So for Matthew 7:1-5, Jesus is telling us not to judge like you are the judge, nor to judge hypocritically.

Does the Bible tells Christians to judge? Yes, but not in a "holier than thou" way or a "hypocrite" way, but with a desire for that person to change his ways and not sin against God (Terminology speaking, this could be call judging, or it could be called point out what someone is doing something wrong. Either way, the Bible speaks about it). Jesus said in (Matthew 18:15-17) that "if your brother sins against you, go and show him his fault, just between the two of you." We are not to judge "by mere appearances, and make a right judgment." (John 7:24) Even for church discipline, Paul has asked the church of Galatia to "restore him gently" when someone is "caught in sin". (Galatians 6:1) Not only to judge others, but also to judge ourselves (2 Corinthians 13:5)

All of this is called Discernment.

I also think that these verses are saying that don't judge others but not allow people to point out your own faults in a similar fashion. If you feel like you can help people by pointing out things they are doing wrong then don't be a hypocrite when they point out things about you that could use improvement and claim that you don't need to change. The mote in their eye (small) compared to the beam in yours (large).

I dislike when people use this verse to say Christians can't judge. Sure, we're not God and it's not up to us to decide who is going to heaven and who isn't.... but the idea that we're not supposed to have opinions on the activities of others is absurd. There are other verses in the Bible that talk about removing sinners who refuse to repent from the Church. That would be a form of judgment too but it's encouraged.

If you're judging in a sanctimonious way then you're setting the standard for your own condemnation, but that doesn't mean we aren't to judge.

Jesus said, "Do not judge according to appearance, but judge with righteous judgment" (John 7:24).

If someone steals, lies, commits, adultery or murder, etc., the Christian can make a (righteous) moral judgment and say the actions were morally wrong, and that these sins will have eternal consequences.

"True tolerance is not a total lack of judgment. It's knowing what should be tolerated--and refusing to tolerate that which shouldn't." -Chuck Colson

I personally don't that your judging someone if you tell them they're wrong. If you know what if right and see they are wrong it is your duty as a christian to tell them so, but also help them to see there wrong doing.

play4fun : I think 1 Corinthians 5:12-13 sums it up nicely; speaking in regard to the church Paul said:

"For what have I to do with judging those also who are outside? Do you not judge those who are inside? But those who are outside God judges. Therefore "put away from yourselves the evil person."

It isn't our job to fix the world. It is our job to share the gospel with the world. Christians don't make the rules for how the world should live, because it seems to be a mistake to endeavor to write Christian legislation. We can't make people holy with laws. They need a change of heart. We can't fix the world by judging it, but rather by introducing them to the One who can change them from the inside. The changed believer will change the world.

On another note though, I think it is important sometimes when sharing the gospel to teach the need for a Savior; while still respecting the person, show them what sin according to the Bible is. As far as judging other Christians "a little leaven leavens the whole lump". Church discipline fails if we neglect to use it, instead ignoring sin within the church, or if we hammer people with their failure and never give them an opportunity to be restored. The goal in all corrective judgment should be restoration of the person towards God, not to make them inferior. As such, like you said, it requires discernment.