Brought Under Catholic Control: The Church exempt from plagiarism?

“I also took from Tyconius — once a Donatist heretic — whatever passages agreed with sound sense. From what was worth keeping, I cut out the excess, hacked away what was out of place, smoothed over what was rough, and brought the whole thing under Catholic control. For I found a great deal in his work that was useless, inappropriate, and flatly contrary to true doctrine — so much so that he had deliberately seized on damaging passages, driven by the wickedness of his own heart, intending to use them to mock and wound our Church. No wonder a heretic twisted the material to suit himself. But whatever he managed to find and strip out, he tried to turn against us unjustly. Our task was to take back those same passages and use them to expose and destroy his error. For just as a precious gem must be picked out of the dung by a careful hand and restored to its rightful place — so wherever Catholic truth shines, even in the mouth of an enemy, it belongs to the Church alone. Whatever truth rings out, even from outside her walls, is hers by right.”

— Primasius of Hadrumetum, Commentariorum in Apocalypsim, Praefatio ad Castorem (A. D. 551)