“Normative” ethical theories

[Lucian]

I don’t see how defining something as moral does any such thing as being useful to compel once one realises that all is what is being done. I am not being nihilistic about airplanes, I am however about supposed facts that somehow obtain for actions that people simply define as being moral or not.
How would you persuade someone that is not convinced of your view of what a moral fact is? What do you appeal to to show the Incan if they still existed that sacrificing people on an altar in a painful fashion is immoral? I don’t see that the realist is any better off than the anti-realist here
What specifically about an act makes it moral or not? Just utility of the label itself in persuading people? Claiming God will punish people does the same and probably with the same degree of success in curtailing or promoting an action as someone claiming morals exist