While I agree with the spirit of allowing people to be disgusting, vile, immoral wretches... I think the problem comes in when those same people who want to play those characters ALSO want the game to applaud their choices.
I love it when people want to think murder, slavery, cruelty, hedonism, etc. is okay but whine about the game judging them for it (and thereby putting judgement at the height of the "evils" list above other acts).
Even the Warden shouldn't escape this (a character the narrative makes "factual" is the only person who can solve the problem) - as most NPCs should have the option to choose Alistair over the player because the player is a villain.
I like games like Fallout that punish you for choosing to be a slaver in one way while rewarding you in another... but tight storylines cannot diverge like emergent storylines can.