You can't be evil if you don't have free will. A tool has no evil except from what comes from the hand that wields it. So to me, orcs make more sense as a constructed organic machine, little better than automatons, and with no moral sense of their own.
This paradox, I.e., if orcs have free will, they can be truely evil, and not just a tool. But if they're predestined to be basically evil as a race, can they really have free will? I think is basically unresolvable. That's why Tolkien could never find a clear answer.