Well, SW fluff has never had much of a reputation for making sense. I know this, because I have binge-trawled Wookiepedia in search of answers to various questions.
One such question was: "Does the Dark Side have any redeeming features?", and the answer was "No. No it fucking does not". The Dark Side even physically manifested as a person at one point (somewhat debatable. As with everything else, It Is A Mystery), and that person was Asshole McMurderboner II, who plotted to murder his own family because they were holding him back from murdering every living thing in the universe.
There's a holocron of "the One Noble Sith", the one dude who apparently lived in a Dark Side nexus (speaking of, why the fuck did Luke decide to 'hide' on an island with a Dark nexus on it? Sith are drawn to those things like flies) without going on a death-and-torture rampage against everything within reach. He only ever played any part in any story because he mastered an otherwise unknown dark art which was later uncovered by a couple more murderbone-prone sith.
What is this art that the Noble Sith perfected and that he performed regularly? The summoning of Dark Wraiths. What are Dark Wraiths? Oh, they're just quasi-physical manifestations of pure fucking hatred, and they're conjured via the lifeforce of someone else so if you slap one enough that it goes away, some random innocent person on the other side of the galaxy will just up and fucking die. Sounds Morally Defensible™ to me!
Yeah. That's legitimately the most stand-up guy they can show off. There's another "WooOOoo Mysterious Gray-Zone Balanced Sensei" character that shows up and says "Maybe there's a way of using the Dark Side while also not being an asshole", but the most she has to show for her ethics is to point to the aforementioned Noble Sith as a positive role model and then induct her first student by torturing him for a few days.
Also, Dooku was criminally underrepresented in the films, despite his dork-ass name. Dude invented a lightsaber form for fuck's sake.