for some reason i think that itachi has always been good from the start. its hard for me to believe that he help kill off his whole clan so that sauske could have a chance to reach MS and take his eyes away from him. itachi must have some other motive if he were to receive sauske's eyes. to kill off madara perhaps? so here's how i think it went down. itachi learns about madara and wants to stop him because he's bad. he can't so he joins him in hopes of growing stronger in the future to defeat him. at the same time he's pumping up sauske so he can become stronger. maybe someday sauske can defeat madara. itachi fights sauske so that sauske could vent out his anger and also to test his ability. at the end itachi is confident that his brother has a chance of defeating madara so he dies and sauske lives. that was my really short version of what i think happened.
the reason i mentioned itachi's white eyes is because symbolism is used a lot in this anime. itachi's white eyes could symbolize that he's a good guy. with those eyes he didn't kill sauske. when he was using the sharingan eyes he wanted to kill sauske.