It is possible to free and effectively save Bruthor and all (or some of) the other inmates without loosing reputation.
First, you should not attack and fight the immaculate jailers in plain sight of the inmates, because Bruthor or the other inmates will become hostile in this case. Same thing as launching an attack on Dreksis and his goblins in the Luculla mines during the quest "Goblin Trouble", the imp Mittix will become hostile in this case.
Second, you will loose reputation only, if a jailor sees you, while you open a jail cell door.
Instead, wait for the right moment and enter Bruthor's cell unseen. If a jailor passes by, he will lock the cell door again, but no repution is lost and no fight starts. Then put a teleportation pyramid in front of Bruthor. He is like an uneducated playful child and uses the pyramid, which teleports him to the other pyramid, which was in my case in the immaculate academy. And no - no cruel jokes with Bruthor, at that time no immaculate was alive anymore in Sacred Stone and I had the prison cell door key of the Enlightened Teacher. Pick up the pyramid and follow him, Bruthor comments something about freedom and his desire to walk around, and some time later he had left that place and was nowhere to be seen.
Now attack and kill all immaculate jailors beside Bruthor's cell, they don't deserve anything better, do they?
Then you may release the other inmates, who will run away immediately. But talk to them before, and in my case, the immaculate prisoner, the woman who was imprisoned after her husband showed mercy with some lost ones, didn't make it to freedom. Jahan teleported her out of her cell, and as a fanatic supporter of the Conduit, she preferred to attack my party and justice was served. It's an RPG after all, deep and with many details.