Perhaps I'm wrong (feel free to stop reading here) but the game issue seems to relate more to freewill than moral code necessarily. The more use of vice, for whatever species, the less control the player retains over the character and in turn the stronger that vice is when used in rolls. I'd assume at some point the character is turned completely to the vice and becomes powerless to resist even against friends? I wouldn't think a moral absolutism is necessarily required, just resisting the particular urges of a species.