It's a shame, but I've not seen many players acknowledge the extraordinary amount of willpower that Cullen must have possessed to withstand everything that was thrown at him during his imprisonment in the Tower. But thinking about it, it has made me wonder something about his character that I hadn't considered before.
There must have been moments during his imprisonment and and torture where he felt his willpower and resolve slipping and given how seriously he takes his vows, duty and beliefs, the knowledge that he too could 'give in' and succumb to demon temptation just as a mage can, would seriously test and shake his faith in himself.
So my wondering is, could that new self awareness that he too was just as susceptible and vulnerable to the 'whisperings and temptations of demons' have externalised itself into his behaviour of towards mages. Perhaps easier to blame them fully than to see himself just as vulnerable.
I'm not sure iff i've made any sense to anyone there, i'm not particularly good at articulating brain thought to keyboard but it's a slightly different way in seeing how the Tower Incident affected him than I usually take.