"Flee sexual immorality." 1Corinthians 6:18 is found in the midst of Paul's correcting the oh-so-open-and-welcoming church in Corinth for allowing a heterosexual church member to remain a church member while having a sexual relationship with his father's wife (apparently not his mother). Paul was clear - demand his immediate repentance (which would requiring stopping the sexual activity or be put out of the church). In 2Corinthians, we learn that the man did repent and the church was now judgmentally refusing to allow his return. Paul corrected them again. The sin had stopped, he should be let back in and the sin should never be mentioned again. 1Corinthians also makes it clear that Christians must judge their fellow church members' lifestyles to assure the church doesn't violate God's standards, but we're not responsible for the rest of the world. Let the dead take care of the dead. Christians must discipline the church.

I'll explain the rest in another post.