Here is the scripture that is used:

"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

Shunning is not meant to be mean but to hope that the person understands how serious it is to leave God and will come back. There are quite a few Christian religions that practice this. I wouldn't say this is an easy thing to practice because it looks to be very difficult. But if a person is very serious about their religious beliefs they will be careful who they are around even if they are family members. Sad but the Bible is very serious about this it seems.