I admire Chomsky but I'm afraid this particular argument isn't very convincing. He merely asserts his position but does nothing (substantial) to defend his position. In what way is moral relativism a logical contradiction? "...even if you’re the most extreme cultural relativist, you are presupposing universal moral values. Those can be discovered.” That's not true at all. I don't presuppose universal moral values. An…
Here's a though experiment, if I blew up the entire planet and left no trace of the existence of humans, did I violate anyone's ethics if there's no one around to be upset? In theory I destroyed ethics too.