I don't think it is enough to split the "dark arts" along the true/false axis. We also need to split along internal/external.

Consider the case that we have tried very hard to avoid being taken in by false arguments and have at long last reached a true and useful conclusion. Now what? We still have to remember our conclusion and refresh it so that it doesn't slowly fade from view. Harder still, if we want our life to change, we need to find emotional equivalents for our intellectual understanding.

So I think that there are good internal uses for the "dark arts". Once you have made your rational decision find a slogan that sticks in the memory and find motivational techniques with personal resonnance, even if they are not entirely honest. Of course, if one has made a mistake with ones initial assessment one is now digging oneself a very deep hole, they aren't called dark arts for nothing.