See this online text:
- “Fraternal Correction, a Help along the Path to Holiness”, by Juan Alonso (July 2010). Available in PDF format (through this page) at Saint Josemaria Escriva.
“[I]f the faith were endangered, a subject ought to rebuke his prelate even publicly. Hence Paul, who was Peter’s subject, rebuked him in public, on account of the imminent danger of scandal concerning faith, and, as the gloss of Augustine says on Galatians 2:11, Peter gave an example to superiors, that if at any time they should happen to stray from the straight path, they should not disdain to be reproved by their subjects…
“[W]hen a man reproves his prelate charitably, it does not follow that he thinks himself any better, but merely that he offers his help to one who, being in the higher position among you, is therefore in greater danger, as Augustine observes….” (St. Thomas Aquinas, Summa Theologica, 2a 2ae, q.33, a.4 ad 2-3, cited by Dave Armstrong)