Gal 2:11 But when Cephas came to Antioch, I opposed him to his face, because he stood condemned.
Act 15:39 And there occurred such a sharp disagreement that they separated from one another, and Barnabas took Mark with him and sailed away to Cyprus.
Gal 6:1, TEV - My brothers, if someone is caught in any kind of wrongdoing, those of you who are spiritual should set him right; but you must do it in a gentle way. And keep an eye on yourselves, so that you will not be tempted, too.
By both his own example and by his words, Paul taught fellow Christians to rebuke/correct and forgive fellow Christians. Gal 2:1-14 illustrates this and directly corresponds to the circumstances described in Act 15:1-41