I meant that you are not to associate with anyone who claims to be a believer yet indulges in sexual sin, or is greedy, or worships idols, or is abusive, or is a drunkard, or cheats people. Don’t even eat with such people. (1 Corinthians 5:11 NLT)
It may sound harsh, but we are commanded to withdraw fellowship from "anyone who claims to be a believer" when they continue to live in open rebellion to the Lord. Obviously, our first commitment should be to restore sinning Christians to a right fellowship with their Lord. But, when they will not repent of their flagrant evils then we must not give tacit approval to their conduct by treating it as if it's no big deal. Sin is to be taken seriously by all of God's people! Until we do this within the body of Christ sin will never be taken seriously by those outside the body of Christ!