Matthew 18 may not apply to getting kicked out of church
18:15 “If your brother sins, go and show him his fault when the two of you are alone. If he listens to you, you have regained your brother. 18:16 But if he does not listen, take one or two others with you, so that at the testimony of two or three witnesses every matter may be established. 18:17 If he refuses to listen to them, tell it to the church. If he refuses to listen to the church, treat him like a Gentile or a tax collector.
18:18 “I tell you the truth, whatever you bind on earth will have been bound in heaven, and whatever you release on earth will have been released in heaven. 18:19 Again, I tell you the truth, if two of you on earth agree about whatever you ask, my Father in heaven will do it for you. 18:20 For where two or three are assembled in my name, I am there among them.”
18:21 Then Peter came to him and said, “Lord, how many times must I forgive my brother who sins against me? As many as seven times?” 18:22 Jesus said to him, “Not seven times, I tell you, but seventy-seven times!
I am really unhappy with the study note in the NET regarding verse 17. To treat him like a Gentile or a tax collector means not to associate with such a person. That's something a Pharisee would write, not Jesus who spent a great deal of time hanging out with these losers. I think v. 22 is the undergirding of this passage as well as the parable that precedes in Matt. 18: 12-14 and the one that follows in Matt. 18:23-35. Forgiveness should come easily because reconciliation is what makes God rejoice. There is no point when we can stop forgiving. There is a point however, in which we stop confronting.
Matthew puts no clarification on what kind of sin to stop and chat with your spiritual sibling about. Some manuscripts add "against you" after "sins" but I'll stick with the shorter reading for these reasons. So if they sin, you go to them and honor their dignity. If they don't listen, bring a couple others in, because they might negate the argument that it's just your problem. If they still don't listen invite the church in on the discussion. The community of Jesus has norms and they need to normalize. If they still won't listen, the church needs to switch their approach from discipleship to evangelism. The tax collectors and Gentiles, were, by default, in Jewish ears, not part of the kingdom of God. Jesus evangelized them and sent his disciples to do that as well, especially after his resurrection, Acts 1:8. If someone won't submit to a church's rebuke, according to Jesus, that person needs to hear the good news again, because it's not sticking. They are loving their sin more than their Lord.
It doesn't sound to me like 1 corinthians 5:11 where Paul gives a list of so-called Christians with whom we should not even eat. For example, I came back from college one break speaking with many foul words interspersed. My younger brother rebuked me and showed me where the bible forbids such talk. I was offended a youngster would rebuke me. But he was right. I needed to repent. God brought me there. My brother practiced Matthew 18 successfully. He didn't run out and find a couple guys minutes after I responded with foulness. He waited. God worked.
Perhaps it would be different if I had been speaking like that loudly in the congregation. Even that could have been handled by a couple guys. I'm glad God is eager to forgive.