I posted a long (10,000+ word) rambling essay on the Dark Arts, Dark Magic, Dark wizards, and the inconsistency with which these various terms seem to be used in the WW on my lj: “Dark Magic Doth Never Prosper.”
http://terri-testing.livejournal.com/28365.html#cutid1What is relevant for looking at “Severus and the Dark Arts” is the central distinction I made: that the portrayal of Dark magic in the Potterverse lacks coherence partly because different groups in the WW are actually using the adjective “dark” in different, and sometimes mutually incompatible, ways.
To recapitulate my main argument (so no one here has to wade through my interminable babble to understand what I want to say about Severus): I posit that in the British WW there are at least three distinct groups applying the adjective “Dark” to magic with different meaning. (Cut here for those who don’t want to read the original.)
( The first group )Which brings me finally to Severus.
( The Dark Arts are a POWERFUL )