Of Orcs and Elves - Mirror Image Opposites or Not?

[Ivriniel]

....so, in a sentence:

Nature-nurture ideas, on the one hand, and ideas about moral relativism on the other. I think, to simply be sentient enough to use the word "rebel" in attribution to Elvendom implies a moral code, quite clearly.

This also, for me, opens a discussion about compassion. Elvish slaying bears no compassion for the deposed, does it? The mirror image opposite, also true of Orcs. They like killing each other.

Where is the wisdom in this? And where, anywhere, does any Elf--the being attributed to the greater wisdom--ever consult with Eru/Illuvatar about the place of Elvish compassion in a bearing towards the slaying of Orc. I would have thought, that at the very least, a compassionate slaying of the Orc, would recognise that the Elf was slaying some facet or feature of the Elf (assuming Orcs were Elves, once).

Or else, the way I see it, the Elf is the greater liar than the Orc. For trying to dissemble motivations--you can't have it both ways, Mr Elf. Either you are, or you are not slaying a part of yourself by slaying the Orc, and if you are not acknowledging this, then how are you morally superior to the Orc?