I think I am using "rhetoric" in a different way than Aristotle. For Aristotle, it was the art of speaking clearly and eloquently to communicate a position. I am using it more in the way people use when they say "empty rhetoric" or "political rhetoric". "Unless you give up your rights, the terrorists have already won" is my idea of an archetypal rhetorical technique. That may not be fair to the field of rhetoric, but I need some word to describe it and I can't think of a better one, so "rhetoric" it is.

Rhetoric is a technique that may be useful to rationalists, but it's not a rationalist technique. Compare the use of force. I may, as a rationalist, decide the best way towards my goal is murdering all who oppose me, in which case I'll want to know techniques like how to use an assault weapon. But there's still something fundamentally shady about the technique of killing people; it may just barely be justified on utilitarian grounds for a sufficiently important goal, but it's one of those things that you use only as a last resort and even then only after agonizing soul-searching. I feel confident saying that the technique of murdering people effectively as a Dark Art.

I feel the same way about rhetoric (by my pessimistic definition). Tricking people into believing things they have no legitimate evidence for can certainly be helpful, but the more people do it the worse the world gets. Not only do people end up with less than maximally accurate beliefs, but every rhetorician needs to promote Dark Side Epistemology in order to keep zir job. And if I use rhetoric, you need to start using rhetoric just to keep up, and sooner or later everyone's beliefs are completely skewed and inaccurate. It's not quite as Dark an Art as force is, and it's much easier to justify, but it's in the same category.

Be careful about using the "rationalists should win" slogan too literally. Martial artists should win too, but that doesn't mean they should take an AK-47 to their next sparring match and blowing their opponent's face off. Martial artists place high value on winning honorably. I see no reason why we shouldn't emulate them.