I've reflected on this some more while reading Pseudo-Dionysius (and concurrently reviewing Russell's four-part series on the nature of evil). I can see both sides. Russell makes an important distinction between the ontological nature of evil and the moral evils we are more familiar with in the world. Metaphysically, then, we may regard evil as a deficit of The Good. But in the real world, there are absolutely people out there who desire evil (they are "male-volent," in that they desire evil (volere male)). So to Dionysius's point, insofar as they exhibit desire, this is in itself intrinsically (ontologically) an expression of The Good at work--however their desires may result in real (moral) evil (that is, suffering) for those of us living in the real (sublunar) world. That's my take, anyways.