First off I want to say if Sasuke had turned "good" then that would be the end of the manga. There has to be a vilan and not just any vilan, one who will not just be defeated because so far most of the "bad guys" are dead: the only two standing are Kabuto & Tobi/Madara. Second I would like to point out how Itachi failed to set the record straight which is all Sasuke really wanted. The one person who is responsible for ALL of Sasuke's turmoil could not spare five minutes to tell him what he needs to know. Itachi wants to leave everything up to Naruto? It makes no sense because so far every time Naruto tries to talk sense into Sasuke it never seems to do the job. Third, yes ninjas are like "soldiers," but what Itachi did was for the wrong reasons. From what I understood he was ordered by the elders to eliminate the Uchiha clan and Danzo was the main person behind it. That is why after killing Danzo Sasuke was satisfied (for a moment). To live your life in a lie, have no one to really guide you, the one person who was family lied to you, tormented you, and at the end he STILL has this distance between you it can cause Sasuke to ignore the "logic" in anything. Now everyone wants him dead, Itachi was no help, and what does he have to loose? Sasuke has nothing to loose and revenge is the only thing he knows.