Actively making your argument objectionable is very different from avoiding the use of the Dark Arts. In fact, arguably it has the same problem that the Dark Arts has, which is that is causes someone to believe something (in this case, the negation of what you want to show) for reasons unrelated to the validity of the supporting argument.

Sorry, I only meant to imply that I had assumed we were discussing rationality, given the low status of the "Dark Arts". Not that there was anything wrong with such discussion; indeed, I'm all for it.