The differences between act utilitarianism and ethical relativism are presented according to moral judgements and what makes an action right.
Act utilitarianism is the view that one ought always act in such a way as to bring about the greatest benefits for the greatest number of persons. Thus, at any given time, one has a duty to choose the act that maximizes benefits and a corresponding duty not to choose any act that does not. In this view, it is hard to see how there can ever be an act that is both permissible to perform and permissible to omit. According to act utilitarianism, one has a duty to act in such a way as to
bring about the greatest benefits for the greatest number of people. One's duty is not to obey some fundamental principle; it is to look to the future and do what is necessary to maximize utility. Act ...
The answer discusses the difference between act utilitarianism and ethical relativism, and that sophists such as Callicles and Gorgias contended that morality was relative and that what was right for one person or group was not necessarily right for another, which is in opposition to act utilitarianism.