The article brings up many interesting points, but does not convince me of the "absolutely" relativist view, either culturally or subjectively. Subjective relativism has major flaws including its impracticality. It would be nice to allow every individual his or her ethics and thus actions, but laws in a society must be made and so there are necessary (and hopefully morally based) rules which everyone must abide.Also, consider the scenario: Person A believes that they are superior due to random biological traits (color, gender, sexuality), they would even go so far as to say, anyone not like them should be enslaved/segregated/killed. Person B is part of the group considered "inferior". Now, B cannot be equal and inferior at the same time.It seems the idea of relativism would experience somewhat of a self-contradiction here, as it by nature assumes all people's views are equal even if the views stand for inequality.Being absolutist perhaps drags with it the unsavory taste of moral superiority and self-righteousness, but I think relativism often leaves a door open for people to just stop thinking about an ethical question, which is not only defeatist but again not practical for defining life in society and human interaction.
I agree with your criticisms of ethical relativism. One problem I have with the essay is its author's apparent assumption that ER is a corrective to ethical absolutism. But if ER is self-refuting or otherwise not viable, then it's not a corrective to anything, but simply another mistaken view of ethics.