It's been said that we shouldn't judge one another. It has also been said we shouldn't point out the sins of others when we know for a fact that, we too, are prone to sin. This is perpetuated by those that like to quote Jesus' own words:
"Stop judging, that you may not be judged. For as you judge, so will you be judged, and the measure with which you measure will be measured out to you. Why do you notice the splinter in your brother's eye, but do not perceive the wooden beam in your own eye? How can you say to your brother, 'Let me remove that splinter from your eye,' while the wooden beam is in your eye? You hypocrite, remove the wooden beam from your eye first; then you will see clearly to remove the splinter from your brother's eye" (Matthew 7:1-5)
Yet, their purpose in quoting this passage is to avoid acknowledging that what they may be doing, could be in fact sinful. In other words, "become ignorant of my sins, so I don't have to feel guilty about them." This leads to the interpretation of "don't judge others, period" whereas this statement is not an outright prohibition of judgment, nor is it a prohibition of addressing the sins of others. Rather it is a statement that addresses hypocrisy in the "holier than thou" sense of the word. True, we are all guilty of sin in one form or another, yet it is equally as important to recognize the sins of others as well as our own.
The Church teaching on this subject is in line with the chief spiritual works of mercy 1,2, and 3 found in The New Saint Joseph Baltimore Catechism:
1) Admonish The Sinner
"It is an act of love to try and make another realize how bad sin is. This can be done by trying to keep them out of sin or an occasion of sin, or by trying to get them to confession afterwards. In cases where we think it might make them worse, we do not correct them directly. We can let them know indirectly, though, especially by our example, that we do not approve of their actions" (Pg. 98)
2) Instruct The Ignorant
It is an act of love to help others in one way or another to learn the truths they need to know to save their souls" (Pg. 98)
3) Counsel The Doubtful
"It is an act of love to help others to be certain about what they should do to love and serve God. For example, answering questions about eating meat on Fridays." (Pg. 98)
If we were not meant to address the sins of others, the teachings of Jesus would have faded in the dustbin of history. The entirety of Christianity is built on the idea of salvation and Jesus is our savior. That is not to say that the sins on our own souls are less deserving of judgment than those sins we see being committed by others. Nor is it to say that we should express pride in whatever virtues we may practice, acting as the Scribes and Pharisees did. However, it was also said by Jesus:
"Go, therefore and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit" (Matthew 28:19)
"Jesus said to Thomas: I am the way and the truth, and the life. No one comes to the Father except through me" (John 14:6)
What good is knowing God's truth, if you willfully withhold it from others to spare their emotions? Jesus gave us the truth in order to profess it to others for the salvation of souls, not to judge or condemn people. Passing judgment is up to God, but it is our duty to our neighbor, that we point them in the direction that leads to him. They may not want to hear it, but to ignore what is, or may be going on, is also a sin
Therefore, whoever knows the right thing to do, yet fails to do it, is guilty of sin. (James 4:17)
By pointing out sin and helping others to avoid the near occasion of sin, we are speaking God's truth and by that truth, we assist them in their journey down the straight and narrow path that leads to heaven. Not because we are more righteous, or more deserving of heaven than they are, but because we love them as children of God and we desire to see them in heaven. Even if we ourselves are unworthy (and we are all unworthy). And wanting salvation for others and guiding them on the right path that leads to God/Heaven, is one of the greatest expressions of love and charity that one can possibly give.