If the disagreement is resolvable, you don't need the dark arts. If you're considering the dark arts, it's purely out of contempt.

If both parties are imperfectly rational, limited use of dark arts can speed things up. The question shouldn't be whether it's possible to present dry facts and logic with no spin, but whether it's efficient. There are certain biases that tend to prevent ideas from even being considered. Using other biases and heuristics to counteract those biases - just to get more alternative explanations to be seriously considered - won't impair or bypass the rationality of the listener.