Excommunication is discussed in several places in the New Testament. So it’s not an issue that can be conveniently ignored.
Matthew 18:15-17: If your brother or sister sins, go and point out their fault, just between the two of you. If they listen to you, you have won them over. But if they will not listen, take one or two others along, so that ‘every matter may be established by the testimony of two or three witnesses.’ If they still refuse to listen, tell it to the church; and if they refuse to listen even to the church, treat them as you would a pagan or a tax collector.
1 Corinthians 5:4-12: So when you are assembled and I am with you in spirit, and the power of our Lord Jesus is present, hand this man over to Satan for the destruction of the flesh, so that his spirit may be saved on the day of the Lord . . . Don’t you know that a little yeast leavens the whole batch of dough? Get rid of the old yeast, so that you may be a new unleavened batch—as you really are. But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people . . . “Expel the wicked person from among you.”
Romans 16:17: I urge you, brothers and sisters, to watch out for those who cause divisions and put obstacles in your way that are contrary to the teaching you have learned. Keep away from them.