[hablyShappY]

Why would it be unethical? Is it because we would be unhappy if we were servants? Consider how some people are happy to work in places that most of us would be incredibly unhappy working in. They choose it. They enjoy it. Perhaps their brain is wired that way, differently from ours. Is it unethical to employ them?

Consider--Dogs have been bred to enjoy serving humans at menial or dangerous tasks for millenia. No one (well, almost no one) considers the use of dogs as working animals to be unethical.

If they were deliberately created to enjoy unpleasant tasks, why would it be unethical to employ them for such tasks? They would not consider themselves to be suffering, so why should we?

I think there's a problem with comparing possibly sentient machines to animals we believe are sentient. When animals feel happy, there is a chemical process that triggers the subjective experience of pleasure and they like it and want more. A robot is simply programmed to act in a certain way. It might be self-aware and have subjective experiences of sight, hearing, etc., but can you possibly determine if a robot is actually happy with its existence and doing what it likes or is it just trapped following a program and basically watching itself behave as a slave? How could you write a program that will allow the robot to signal that it is having a subjective experience?