They would be pretty p!sssed off, just like anyone else. If you think that this "argument" is a refutation of moral relativism, you obviously do not understand it.
Most moral relativist have simply abstracted themselves from the real world and just need a good dose of it to wake up. Few of them make convincing arguments, because after they deconstructed morality, they proceeded to deconstruct reason. And we know what becomes of argument without reason. And your blanket statement that it has eluded philosophers for millenia is simply ridicilous.
Blah, blah blah. I'm waiting for a refutation of moral relativism. So far, I haven't seen one, either in this forum or in any of the writings I read getting my bachelors and masters degrees in philosophy from well-regarded schools. If you have one, I'd be very interested to see it.
hmmm. . .
The arguments against moral relativism are in truth very difficult to make. And it is an old, very old argument. You can trace its origins back to the origins of philosophy.
I am hardly prepared to make such an argument, but I do stand by my assertion that a good dose of reality would wake many moral relativists up. You see no moral relatavist has ever defended Hitler's holocaust, at least openly. And a moral relativist cannot objectively say that Hitler was wrong. You see, it is my opinion that an understanding of moral truths requires more than a knowledge intellectual, abstracted from the physical. Morality is rooted in our mortality and in physical necessity. The intellect left purely to the abstract cannot discern it. At least that is my opinion without great argument.
And to reveal something about my own life, I left a PhD program precisely during the search for the grounds of morality. A professor of mine shook what I thought were the surest rational grounds for ethics. Having left academia, I realized that the intellect left completely to itself can tear itself away from the human condition.