Note the word used by Paul is majority but not everyone, which means there were some who didn't shun a wrongdoer:
6 The punishment inflicted on him by the majority is sufficient for him."
So not everyone followed Paul's previous request that they shun the wrongdoer in Corinth, they were not in anyway scolded or punished for not doing what he had said, and this shows that although he had been given authority by some of the congregations to "order" Timothy and other workers to do this and that, he did not have dictatorial powers to order every Christian to shun a person. He could suggest it but each was left to his or her own conscience to decide if to do so. Galatians says we are all equals before God, all imperfect humans who would not be resurrected except for God's gracious kindness and the sacrifice His son made of his human life.