I mentioned this quest before as an exception, it happend, but for sure there are also non force users who hunt civilians and murder them for fun, criminals in this or other form. and in my story
. Also, if the Sith were powerful and useful ( althou we dont know much about them, at least I dont know ) then sacrificing few citizens for sating their bloodlust is a rather fair price, althou it should be much better covered.
and someone above said that Empire is dictatorship - Empire is a monarchy