I think it's probably hard to find a belief with many adherents which nobody tries to promote using dark arts. If you find that one of your deeply held beliefs is more commonly promoted with dark arts than without, that should definitely raise alarms.

I don't see these as dark arts. Self-affirmation doesn't make people more likely to believe just any old thing, it makes them feel less threatened so they're more willing to consider something that they would otherwise reject out of defensiveness.