He won't gain more, he'll gain differents things , like any other game where you can kill or steal (TES,...), it's just a player choice. If he wants to be righteous he can , and if he wants to be a bast**d he can too , can't see where's your matter with this kind of people.
Anyway, he was talking 'bout the NPC's will of life , who seems to disappear when he killed ahru. I didn't try to kill him, will try that tonight and tell ya, seems strange.
Oh and your part on raping/torturing sounds a bit silly , even if other video games have already made it ( you said GTA, and one who was like a western, can't really remember the name).
So please, let people play like they want to.