I'm firmly against the idea of Internet arguments presenting an opposing position under the guise of it not being their actual opinion so they can run away from debate. Devil's advocate is a technique that should be used in school to learn how to make stronger arguments.

All it does is covertly promote the idea by presenting it as reasonable and on an equal level to the other idea. While at the same time being able to shut down debate, by pretending they don't actually think that.

Anybody can say something like "but what about the good side of the African slave trade" but they will be debated and the argument shut down if they present it as their actual argument and engage in good faith with the comments. Using the devil's advocate technique is an extremely useful way to argue in bad faith, anonymously on the Internet.

Critique of the author's style is fine. An opposing view should honestly be presented as such.