Matthew 18:15-17
[i]15 If your brother sins against you, go and show him his fault, just between the two of you. If he listens to you, you have won your brother over.

16 But if he will not listen, take one or two others along, so that ‘every matter may be established by the testimony of two or three witnesses.’

17 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.
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I think too many view treating others as tax collectors and pagans equates to shunning them. While, in the days of Paul, that might well have been an option, and could be what he was getting at, as the community gathering was needed for survival, yet today, if someone is shunned, they simple go to the church down the street, or even to the local bar.

Rather, in treating someone as such, we should dialog, and pray for them. We explain how they are wrong in love, and pray that they may return to the fold.

If we look in Acts 17, Paul talks about walking in a city of idols, and what does he do? He spends time with them, gets to know them, and complements them, and then addresses the problem. He has built a connection with them in love first, and then he tells them of the Truth.