I agree that the term "self-defense" is often abused, but in the context of the player character's life in BG1 and 2 I can't remember any mandatory uses of deadly force that don't fit into that term. Maybe the killing of the whore-house guards, but even that can be skipped without using out of character knowledge. ToB is more problematic; you have no choice but to kill the 5, and you can't completely avoid killing their troops. Even then, they have made an unprovoked attempt on CHANAME's life, and can reasonably be expeted to do so again even if CHANAME flees.EDIT: @ Bob: To be legally granted a right does not make it morally acceptable per se. The context for self-defense is rather limited. I wholeheartedly subscribe to self-defense in the personal context, but this argument has been abused for far to many preemptive actions by larger groups which are debatable.
In the context of the mod, I can't see any actions taken by a well played non-evil PC on the same level as the actions taken by Irenicus.