Immorality was part of the culture of Corinth; it had come along with new believers when they came to Christ and became part of the church. The church leaders had been reluctant to interfere with the 'personal lives' of their members. But Paul had previously told them to deal with people who persisted in sinful behaviour by withdrawing from fellowship with them. The pain of spiritual isolation was designed to bring sinners to their senses and help them to see that they must repent.
 
It appears that the church had interpreted that as meaning that they must not associate with wicked unbelievers. But as Paul pointed out, that would defeat the principle of evangelism. The gospel is designed for sinners and they need to hear it from their Christian friends. Refusing to meet the people who most need the saving grace of Christ is completely against what Christ taught and practised. Neither is it the Christian's role to judge the world. Christ alone has that responsibility (Acts 17:30).
 
No; discipline was to be a way of stirring the conscience of the true believer. While sweet Christian fellowship surrounded the offender he was being led to think that his behaviour was acceptable. Withdrawal of that privilege is the ultimate leadership sanction: a responsibility which is still essential.
 
Failure to see fellowship as an honour given by God to His children is a serious failure in some churches. Leaders are so keen to increase their memberships, tying them into serving in church activities, that they cannot see that their workforce needs to be committed firstly to following Jesus. Like Ananias and Sapphira (Acts 5:1-11) and Elymas (Acts 13:8-12), if they thought they could do without the Lord, the Lord could do without them. It is serious stuff. Pray for your leaders that they will have the necessary boldness to be faithful to their Master as they exercise discipline when believers refuse to repent.