BDSM is literally one of the things I believe Ralph likes doing to the girls, and at least a few of them like that being done to them. Angelica I remember being a more extreme case in that she's basically your doormat, and gets pissed at people for not agreeing with you. In fact, light or dark path, there's literally no way she isn't getting pissy with at least someone due to not listening to you. The only difference is her reverence of you. Do you want her to see you as a king, or as a god?
I feel like just having slavery as a theme should have told the more vanilla viewers that this game was anything but kind, and from my point of view, if a dev makes a slave game, I fully expect something dark in it just to solidify that these girls have no real will of their own, just maybe the fact there's some kindness sprinkled in if the player so chooses. The act of being a slave is not vanilla.