Thank you. And in answer to your question - nothing. There is a British TV show named for what was going on "keeping up appearances". The actions taken by the errant sects in abusing Donatus who was in the right necessitated the revisionism and all the flourishes that go with it. The more bold the lie, the more likely it is to be bought. It should shock no one that the only source from which it is known what the Donatists were presumably teaching is the group that had them wiped out. The mistake they made is that they apparently didn't have access to change the secular record or never got around to it.. Constantine was wrong from ignorance. The church was wrong due to purposed rebellion against the word of God - purposed in that they largely were not of a mind to be counted amoung those thrown into the fiery furnace if you'll forgive the dark humor in the allusion. The people weren't stupid, they were untaught and gullible. And given enough information, most of their leaders would have been swinging from tall trees for this brazen injustice. With the level of political intrigue going on at the time, I'm amazed Constantine didn't murder more people than he did to keep the threat against his throne quelled. And in the end, the institution he gave birth to through his errors defrauded even him. That, to me, is divine irony if not justice. At the very least, the croc ate him last.
He established them as the only orthodox, legal church. Sainthood is the least they could do to return the favor. ;o)