If everything is perfectly simulated, the rules that allow consciousness to emerge are also there, and thus consciousness would emerge, regardless of whether it's a simulation or reality. If we only simulate a consciousness without laws of reality, that consciousness would still be designed to mimic a consciousness from a reality with laws (ours), and since it would be a perfect simulation (and it would have to be so in order to run meaningful tests), that consciousness might as well be as real as us. Thus, unethical.