Re: To the people who think itachi is guilty of his choices. (Read)
He had two choices:
1: Kill his whole clan and prevent thousands of dying from a great ninja war, and have his brother to live on as a survivor to restore his clan. Also keeping the hidden leaf in great shape. Also suffer so much to the point that he would die because of his own guilt (His guilt is what turned him so sick).
Here's the thing, and I don't know if Kishi intended this from the very beginning or if get got caught into some kind of a trap trying to turn Itachi (a very popular character) into a secret good guy after already laying the ground-work: You don't need to massacre EVERYBODY in a clan to prevent a rebellion.
How many people were in the Uchiha clan? I don't know exact numbers, but they had a whole section of the village to themselves. Even if it were more than 50 people you would expect there to be at least one pregnant woman or at least one newborn baby. Did Itachi kill all of those too? Maybe the Uchiha have some sort of weird mating season that wasn't there yet and there were no pregnant women and no babies, but then were there any children? Was Sasuke the only Uchiha child in the entire village? I find that hard to believe.
Let's say that the fighters in the clan, the combat-ready men and women all wanted rebellion. There still had to be other people there who weren't a combat threat: The elderly, the children, the artists, bakers, builders, teachers. There would have been large groups of Uchiha people around who weren't combatants and who posed no threat to the village.
My point is this: All you have to do to stop rebellion is to kill the people who are potential combatants. Everybody else you kill is an innocent and that's murder. If Itachi just killed the combatants he might have been able to be a hero. However, if he killed innocent non-combatants, he's a cold-blooded murderer.
Itachi did leave Sasuke alive. So either Itachi disobeyed orders a little and could have disobeyed the more, or his orders from Danzo DIDN'T require him to kill everybody. In either case, Itachi could have spared more lives, and he didn't. The fact that Sasuke survived the massacre and was allowed to stay alive by Danzo afterwards proves that it was possible for Uchiha children to have survived the massacre and Itachi chose not to do that.
MAYBE, as a potential second option, Itachi didn't kill the women and children and non-combatants. Maybe Madara/Tobi did that while Itachi wasn't watching and Itachi didn't know. That is POSSIBLE, but Itachi never mentioned it before.
If you want to stop a rebellion you can choose to kill the top 5 people in charge of it, or the top 20 or the top 5 or whatever. Killing women, children and non-combatants doesn't help after you've already killed the people in charge. After that, you're just a murderer and what you've done is not a good thing anymore.