A few weeks ago I discovered the “Dark Is Not Evil” trope and found the TV Tropes page really insightful:
This trope can be a subversion or aversion of several other tropes depending on how it’s played, including Beauty Equals Goodness, Always Chaotic Evil, and Colour-Coded for Your Convenience. A common use for it is for the “Don’t judge a book by its cover” Aesop. It can also be used to promote Evil Is Cool, and sometimes Even Evil Has Standards, except without the, uh… evil. Even though with the subtle (or not so) undertone of Humans Are Bastards that this trope implies, using this does not automatically enforce Light Is Not Good; in fact, stories where Light Is Good and Dark Is Not Evil are quite common.
It’s amazing what centuries of language shifts and political dominance by the ruling classes can do.