Anakin still would have gone Dark. Nothing was stopping that. Sideous was a father figure to him and watching him being struck down would have fueled his hate further. I think he would have continued his dark training somehow. Even if it was in the way that Sideous shrouded the dark side to keep hidden from the Jedi. Anakin was corrupt in AOTC when he decided to give into his anger and strike down all of those Tuskens. He also already had dislike for Obi during those times as he felt he was being held back. Again, feelings of which all lead to hate.
The only thing that would have changed, was who the puppet master was during the original trilogy, Story line.
I think many people will do the same to those Tuskens if they were on Anakin's position.