when and where? from my playthros I can say that in fact there was one such accident. Siths generally dont wander cities seeking for victims, they dont even abuse that much power, and comparing to regular soldiers who kill theyr subordinates for failures I would say that they are rather balanced. Of course that they kill each other from time to time to get a better title or just to get ride of those they dislike but that is purely Sith Code, official relligion of the Sith Empire.
what about that mission where the sith got tagged because they were hunting people down just because it was Tuesday?