If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, treat him as you would a pagan or a tax collector.
At first, it appears as if Jesus is saying to give up on the person, after you've done all that you could. We naturally interpret it to mean that we judge and condemn him as an outsider because our minds are fallen.
However with the mind of Christ, tax collectors and pagans (nonbelievers) are to be sought after and loved more than those in the church.
Think about it. How did Jesus Christ treat tax collectors and pagans? He ate with them (Luke 5:30, Mark 2:17). He forgave their sins. (Luke 9:1-10) He said to them, "Come, follow me." (Mark 2:14) Jesus did not abandon or condemn pagans or tax collectors, but sought after them. He didn't give up on them.
So, if a brother (using the mind of Christ, According to Jesus a brother is a Christian (Mark 3:35) remains unrepentant even after showing him his fault, he is not a Christian until he repents. However, do not give up on him! For it is those who are fallen away then deserve most of our attention. We love them more, not less, when they stray. For I tell you the truth, there is more rejoicing in heaven over one sinner who repents than 99 righteous who do not need to repent. (Luke 15:7)