uther didn’t wake up one day and go “hmm yes let me commit to a lifetime of repression and bad decisions” no. this man was in LOVE. with TWO MEN. who both said no. and one of them had magic. and the other ENABLED it.
like imagine being uther, king of camelot, used to getting everything he wants, and then balinor is out here choosing the forest and dragons over him, and gaius is like “actually i think ethics matter” and also not choosing him??? so what does he do? bans magic. because if he can’t have balinor, no one gets magic. if gaius won’t stand beside him like that, then gaius will stand behind him.
the great purge isn’t just paranoia or grief or even fear. it’s bitterness. it’s “you didn’t choose me, so i will destroy the thing that made you not choose me.” and then he spends the rest of his life surrounded by ghosts of the people he loved but couldn’t control.