I guess I'm for persuasion, think the ends justify in this case. Otherwise you're all bringing knives to a gunfight and crying foul when you get shot down. Could there be a degree of "sour grapes" here resulting from finding one's self inexplicably unpersuasive next to a velvet tongued dummy? Are we sure we eschew the tactics of rhetoric because they're wrong? Is it even fair to describe "dark arts" as wrong?

I say rather that speech is meant to be persuasive. Better speech would then be more persuasive. As such persuasion backed by truth should be sturdier than mere naked truth, which is only palatable to connoisseurs who like their facts without sauce. Have I mixed enough metaphors for you there?

I think thought, hence communication, is highly model based, so you can be compelling with a metaphor that "fits" and one that's well chosen would fit very well indeed. Then the topic under discussion gets a piggyback ride from the metaphor and the stipulated conclusion from the model is transferred to the new topic. (there must be an established name for that sort of trick?) But what if it's in defense of the truth? I say it's ok. To go back to the first metaphor: you gotta fight fire with fire; facts burn too easily.