Sacred Haven of Debauchery

Yeah, right.

Red dialogue? The ones marked in red? Have you ever wondered why they are marked that way?
Wait, I get it. Blue is a compromise, but red is sometimes a loud cry: "IN THE NAME OF FAITH!" and the killing of a vile apostate. Is that what you meant by a good choice?

Decent people don't hide a blood mage, and certainly don't supply him with books from places he doesn't have access to.

Blood magic is just magic, like any other, only much more powerful. Magic is a tool that can be used for the common good. Orsino was unaware of Quentin's madness and believed he was helping him regain lost knowledge, which could prove useful. Considering that during the dialogue, Quentin didn't foam at the mouth, didn't roll his eyes, and, in general, if you think about it, managed to lure several women into a trap without attracting much attention, it's hardly fair to accuse Orsino of being oblivious, let alone stupid.