The sixteen years between 715 and 731 saw the reign of Pope St. Gregory II. At the time, the Emperor of the Eastern Roman Empire, Leo III the Isaurian, left the Catholic Church and followed the doctrine of iconoclasm.
He issued a decree forbidding the use of sacred images. St. Gregory corresponded with the emperor through a series of letters in which he urged him to give up his heresy. Seeing that the emperor was unmovable, St. Gregory wrote to him:
" The pious Emperors were submissive to the Pontiffs of the Church and never dishonored them. You, on the contrary, since the day when you apostatized from the Faith incur that same curse you made against those who persecute sacred ministers...I pray God to give you prudence and repentance so that you will return to the truth that you left and bring the people to the bosom of the Catholic church."
These seem like harsh words for a Pope to say to an Emperor. However, Pope Gregory being a pope and a saint understood the enormous responsibility that an emperor has to lead his people in the Truth. If the emperor is a heretic, he can bring many souls to perdition by his example and by his erroneous decrees, and put his own soul in peril.
Therefore, St. Gregory had an obligation to make clear in very strong language what was at stake. And he did. This is the action of a saint who does what is necessary for the salvation of his flock, even if he is not popular in doing so. Heresy should always be denounced because if left unchecked it contaminates souls with errors that produce rebellion against God and spreads like wildfire throughout the population and their progeny. One need only to note the action of King Henry the 8th and Luther.
Let us ask St. Gregory II to give us the prudence to act against error, to combat heresy and to oppose present day relativism.