[Marileangorifurnimaluim]

Tolkien implies pretty clearly in the Silm that the orcs are elves of the Avari who were captured by Morgoth. That would make their fea elven. Sad thought.

I don't think there is any justifiable homicide in the LotR. Necessary and unfortunate homicide. But not justifiable. No, that just wasn't Tolkien's way. Note the pity for Gollum he urged. And "I pity even his slaves." Not to chide here, just an observation.