‘A man that is an heretick after the first and second admonition reject.’ The subject hasn't changed in a way.
You think of some World War II generals. There are some you read about who had various flaws in their approach, and their staff officers and their subordinates couldn't contain them and persuade them, and this one flaw they had would lead to many thousands of losses and casualties on their own side. When the books are written, the history is written, that particular general, who had quite a reputation, fails with hindsight, and it is really reckoned up: the trouble he caused, as well as the success he had. His flaw brought him down. He wouldn't listen. He was an expensive general.
Or you could illustrate it with an athlete. He is brilliant, but he has got a knee injury, so he is not going to do well. He is still the same person; he has the same powers and abilities, but one part of him is out of kilter, out of function, and that ruins everything. That is the part that pride can play. If you do have strong intellectual equipment, be careful. The devil may have you marked out as a candidate. ‘I can use that man; I can use that woman, so that I can fan back to life his pre-conversion dominating pride, and make him a ruin to himself, to others, and he may be a thorn in the side of the church all his life.’ Very sad! One failing ruins everything. So that's what you have here: ‘a man that is an heretic [a divider, a party former], after the first and second admonition, reject [shun]’, because the fellowship is all-important. The Lord wants the church walking in fellowship, and in love and in harmony: a family of God's people, a true local church, and the person who is going to ruin everything may have to be rejected.