I'm actually of the opinion that anything that is anonymous and thus can't be traced back to your nation is fair play. We are talking about becomming the one true god here after all. Sometimes you just have to dirty your hands. Erm, I mean the hands of some mad, rogue, underling you've never heard of. Of course, most of the time you are friendly with someone you have a NAP with and thus there is no reason to bombard them with nasty spells, but if the situation calls for it, I don't see why you'd refrain from using them.
Of course, the flip side of this is that if the target of these spells suspects it's you who cast those spells, he probably will be mildly annoyed with you
