It is a work of charity to shout: “Here is the wolf!” when it enters the flock or anywhere else.

"The declared enemies of God and His Church, heretics and schismatics, must be criticized as much as possible, as long as truth is not denied. It is a work of charity to shout: 'Here is the wolf!' when it enters the flock or anywhere else.
--St. Francis de Sales, Introduction to the Devout Life, Part III, Chapter 29