Legally there is slavery in some nations. That doesn't mean you should buy into those value systems. I don't mind putting those aside either.
The moral system of values could theoretically be nearly anything. In the drowning man example say I value the reduction of CO2 emissions and view the human race as harmful to that goal I could see the drowning man as beneficial to society even so far as to feel an obligation to ensure that he drowns. Alternatively, I could view the reduction of CO2 emissions as an essential duty of all mankind requiring the work of every human possible thus prompting an obligation to rescue the man drowning. In practice, however, there is a rather narrow range of possibilities consistent with the successful navigation of reality across a lifespan though these can be altered somewhat on a conscious level over that time.