4 Moreover, in polemical discussions, care should be taken not to overstep those just limits that justice and charity alike mark out, and not rashly to throw blame or suspicion upon men otherwise devoted to the doctrines of the Church; and, above all, upon those who in the Church itself are raised to dignity and power. We deplore that this has been done in your case, Dear Son, who, in your quality of archbishop, administer the diocese of Malines; and who, for your signal services to the Church, and for your zeal in defending Catholic doctrine, have been judged worthy by our Predecessor of blessed memory, Pius IX., to take a place in the College of most Eminent Cardinals. It is manifest that the facility with which unfounded accusations are levelled vaguely against one's neighbour, does injury to the good name of others, and weakens the bonds of charity; and that it outrages those "whom the Holy Ghost has placed to govern the Church of God." For this reason do we desire with all our power, and hereby most seriously enjoin, that Catholics abstain from this conduct. Let it suffice to them to remember that it is to the Apostolic See and to the Roman Pontiff, to whom all have access, that has been confided the charge of defending everywhere Catholic truths, and of watching that no error whatsoever, capable of doing injury to the doctrine of faith and morals, or apparently in contradiction with it, be spread or propagated in the Church.
Source: Licet Multa (Vatican.va)