Today’s saint was renowned for explaining why Christianity is the right and true religion and why he was a Christian (the work of an apologist). [By the way, this helps explain the difference between an apology and saying “I’m sorry”–an apology is an explanation of why things happened the way they did, whereas the other is stating one’s regret; I prefer sorrys to apologies, but that’s just me.]
So Apollinaris apparently went after the Encratites, whom he labelled as heretics. You might wonder, “Who were the Encratites?” Here’s the thing about most of the ancient heretics–nothing whatsoever exists of their own thoughts or writings, because the orthodox church folk thought it best to destroy any trace of them and to tell the orthodox’s own version of the heretics’ beliefs. This is in the vein of “victors write the histories.”
From what has been pieced together, the heretical Encratites believed in such horrid things as vegetarianism, drinking water (i.e., abstaining from alcohol), and staying unmarried. Oh, and they were not enthusiastic about Paul’s epistles, either.
Apollinaris didn’t stop there, either. He also called out (i.e., “damned”) the Montanists, another heretical group who actually believed that the Holy Spirit could call anyone (male or female, rich or poor, educated or not) to any role (prophet, pastor, teacher), and that there was a qualitative difference between institutionalism and the work of God.
So the Encratites and the Montanists are gone, and Apollinaris is a saint, forever ensconced on the calendar of saints.