Empire itself is a stability and order, so whenever it grip reaches, subjects become part of order. Killing for failures is essential to get rid of weak and useless material that may cause even bigger havoc if spared. Sith does not kill for the wrong look, unless it is in public, and someone openly disrespect them, manifestation of power is required. Those who think that something is wrong are usually less intelligent people with weak characters that want to be equal with others just for the sake of it, typical and dangerous.
Absolute power rarely leads to corruption, but such statements are well known for people who try to remain within heart of corruption in democratic states of Republic. It is ill propaganda manufactured to liking of simple folk who feel entitled to rule their countries whenether they cant count to 10 or are simply idiots ( rarely individual agrees to his intelectual limitations ).
Republic is based on corruption, semi mob rule where senate live on bribes. Republic is negation of advancement for the sake of unnatural ideals.
only the most intelligent, powerful and with proper personality people deserve to rule ( about 1% of whole population ) - and that is The Sith Empire, place where everybody seeks challenge, advancement and further development.
The Sith Empire, place that you want to die for ( and most probably you will )
I recall the Empire living off bribes as well. I believe it was a Sith Acolyte who wants to bribe you to stop her Master from proving that all living things can have the force.
The same with another Sith (Lord I believe this time) that wishes to bribe you to keep secret that Jawas are infact capable of using the force and then act like it never happened.