If the slaver is a human, other humans will judge them by human standards. Keeping the slaves ignorant of their condition and alternatives should not make it any more acceptable (if for nothing else since that is something you could easily replicate with human slaves by raising them as slaves).

> Why would using math in certain fashion such that it mimics consciousness be considered unethical and comparable to human slavery?

If it is really conscious, it should have rights. Why? Because it's a person, with thoughts and experiences, and we're not evil and deprive persons of their right to self-determination because it's convenient to us.