15 Lastly it is most important that those who defend the interests of religion in the press, and particularly in the daily papers, should take up the same attitude. We are aware of the objects they strive to attain and the intentions with which they have entered the arena, and We cannot but concede to them well-earned praise for their good service to the Catholic religion. But so lofty, so noble, is the cause to which they have devoted themselves, that it exacts from the defenders of truth and justice a rigorous observance of numerous duties which they must not fail to fulfil; and in seeking to accomplish some of these, the others must not be neglected. The admonitions, therefore, which we have given to associations, We likewise give to writers; We exhort them to remove all dissensions by their gentleness and moderation, and to preserve concord amongst themselves and in the people, for the influence of writers is great on either side. But nothing can be more opposed to concord than biting words, rash judgments, or perfidious insinuations, and everything of this kind should be shunned with the greatest care and held in the utmost abhorrence. A discussion in which are concerned the sacred rights of the Church and the doctrines of the Catholic religion should not be acrimonious, but calm and temperate; it is weight of reasoning, and not violence and bitterness of language, which must win victory for the Catholic writer.
Source: Cum Multa (Vatican.va)