III. All the bishops of Christendom agree with him in this.
Therefore in addressing our most Christian Emperor, who is worthy to be classed among the champions of Christ, I use the freedom of the Catholic Faith and fearlessly exhort you to throw in your lot with Apostles and Prophets; firmly to despise and reject those who have deprived themselves of their Christian name, and not to let blasphemous parricides, who, it is agreed, wish to annul the Faith, discuss that Faith under treacherous pretexts. For since the Lord has enriched your clemency with such insight into His mystery, you ought unhesitatingly to consider that the kingly power has been conferred on you not for the governance of the world alone but more especially for the guardianship of the Church: that by quelling wicked attempts you may both defend that which has been rightly decreed, and restore true peace where there has been disturbance, that is to say by deposing usurpers of the rights of others and reinstating the ancient Faith in the See of Alexandria, that by your reforms God's wrath may be appeased, and so He take not vengeance for their doings on a people hitherto religious, but forgive them. Set before the eyes of your heart, venerable Emperor, the fact that all the Lord's priests which are in all the world, are beseeching you on behalf of that Faith, wherein is Redemption for the whole world. In which those maintainers of the Apostolic Faith more particularly appeal to you who have presided over the Church of Alexandria, entreating your Majesty not to allow heretics who have rightfully been condemned for their perversity, to continue in their usurpation; for, whether you look at the wickedness of their error or consider the deed which their madness has perpetrated, not only are they unable to be admitted to the dignity of the priesthood, but they even deserve to be cut off from the name of Christian. For— and I entreat your Majesty's forgiveness for saying so— they to some extent dim your own splendour, most glorious Emperor, when such treacherous parricides dare to ask for that which even the guiltless could not lawfully obtain.
Source: Letters (New Advent)