1 Corinthians 5:3-5; 1 Corinthians 5:13
I'll tell you what I would do. Even though I'm not there in person, consider me right there with you, because I can fully see what's going on. I'm telling you that this is wrong. You must not simply look the other way and hope it goes away on its own. Bring it out in the open and deal with it in the authority of Jesus our Master.
Assemble the community - I'll be present in spirit with you and our Master Jesus will be present in power.
Hold this man's conduct up to public scrutiny. Let him defend it if he can! But if he can't, then out with him! It will be totally devastating to him, of course, and embarrassing to you. But better devastation and embarrassment than damnation. You want him on his feet and forgiven before the Master on the Day of Judgment.
God decides on the outsiders, but we need to decide when our brothers and sisters are out of line and, if necessary, clean house.