By a Dark Arts practitioner, I just mean someone who uses rhetorical techniques to win debate points, without particular regard for the truth.
So whether a rhetorical technique should be classified as Dark Arts is determined by the intent of the speaker?
Sometimes you just need to say something is straightforwardly wrong
That's not a problem, you can say whatever you want. The issue is whether you should attempt to impose your morality, by force if necessary, on another human who doesn't agree with it. In the case of conflicting moralities, which one wins? Historically, the answer to that is "the one with the bigger guns" which is... an interesting observation.
So whether a rhetorical technique should be classified as Dark Arts is determined by the intent of the speaker?
I'd agree with that for the right definition of "intent". It's hard to have much "art" on accident, and without the optimization for persuasion over/against truth it starts to look a lot more like "bad reasoning that isn't necessarily obviously bad to people who also reason bad"
Besides, I really wouldn't want to fall in the trap of saying "well yeah, everyone finds your arguments more persuasive, but you're us...
Recently, James_Miller posted a conversation between Sam Harris and Scott Adams about Donald Trump. James_Miller titled it "a model rationalist disagreement". While I agree that the tone in which the conversation was conducted was helpful, I think Scott Adams is a top practitioner of the Dark Arts. Indeed, he often prides himself on his persuasion ability. To me, he is very far from a model for a rationalist, and he is the kind of figure we rationalists should know how to fight against.
Here are some techniques that Adams uses:
Overall, I think what Adams is doing is wrong. He is an ethical and epistemological relativist: he does not seem to believe in truth or in morality. At the very least, he does not care about what is true and false and what is right and wrong. He exploits his relativism to push his agenda, which is blindingly clear: support Trump.
(Note: I wanted to work on this essay more carefully, and find out all the different ways in which Adams subverts the truth and sound reasoning. I also wanted to cite more clearly the problematic passages from the conversations. But I don't have the time. So I relied on memory and highlighted the Dark Arts moves that struck me immediately. So please, contribute in the comments with your own observations about the Dark Arts involved here.)