There are some important principles in chapter 5. The first is Paul's admonition regarding a flagrant case of sexual immorality in the church. A man is has taken his father's wife. This does not mean the woman is his mother (although possible) but under the law code of the Hebrew Scriptures this is clearly and consistently forbidden. It is not an issue Jesus address in any specific way and so the early church's understanding was that such behavior was still forbidden. The problem is that the Corinthian church has chosen to boast about their "freedom" and "grace" rather than confronting the man with his behavior (not to mention his father's wife).
Paul makes a distinction in 5:9ff between judging the behavior of those who claim to be Christ followers and judging the behavior of those who are not claiming to be Christ followers. We are not to judge the behavior of those who do not belong to Christ. We are to love them, walk with them and our encouragement of them is not "clean up your act" but "come to Jesus." A friend of mine once said that Jesus never cleans his fish before he catches them. It is up to Jesus to bring conviction and correction to the life of one living immorally. However, if we claim to be Christians we have a responsibility to live up to a different standard. In modern America this is profoundly difficult. Research consistently shows that there is minimal difference in the ethics and behavior of those who claim to be Christian and those who do not. Divorce rates among those who claim to be Christians is no lower than the national norm and instances of alcoholism and infidelity run about the same. I have often thought that in modern American we have as many non or nominal Christians inside the church on a Sunday as we do outside the church on a Sunday. How do we handle these confrontations today?
I have come to believe that I must earn the right to speak into someone's life. Just become someone comes to church on a regular basis does not mean that they are committed to following Jesus nor is it an automatic indicator that they intend to do so. It is only in convenental relationships that we have permission to speak into peoples lives. In my covenant group we strive to hold each other accountable and when one of us is off the rails a bit the group confronts and strives to bring them back.
I have also come to believe that the church is open and available for everyone -- regardless of what they are doing or where they come from. However, leadership in the church is an entirely different matter. What behaviors should be considered "forbidden" for leaders? What "immoralities" should be confronted? For the first century Corinthian Church, they were choosing to live by the same standards as the world around them (and, in this one specific case, at an even lower standard than society around them). As we shall see in the next chapter (on Monday) this is not the only issue they struggled with.
Finally notice that is not just the sexual immorality that Paul wants us to take notice of: he adds "greedy" "idolater" "reviler" "drunkard" and "robber" to the list. We tend to focus on the "hot" sins like sexual immorality and neglect the deadlier behaviors of greed, idolatry, putting others down, conspicuous consumption and wrongfully taking from others. . .