idk because anyway is the only one
Okay... We know that Madara hates Konoha's guts. But if he hates it so much, so so much to release the nine-tailed on it, why in God's name did he agreed with Senju to create Konoha anyway?
We know that the Uchiha's back then were more then ready to fight and kill the Senju clan till death. Yet madara, the one who wants to destroy what he created, set peace with the enemy and let Senju be the 1th Hokage. Not only that he, as in Madara, let the Uchiha's be Konoha's police.
My point is, why did he want to kill that what he himself created? Something didn't go for HIS favor, but that same something wasn't reason enough to let all the other Uchiha's turn against the village. Now he was alone and has the eternal MS. What does he do?
Release the Kyuubi on the village.
Madara on this moment has no reason to lie to Sasuke. He will mind **** the poor boy with the very truth. Maybe he DOES leave certain important things out of his story, but he got to have the young Uchiha's trust in this.
Itachi tried to protect Sasuke to keep him from Madara. Wich was poorly done, if Itachi wanted Sasuke far away from him, why mention him at all. So, it wasn't only protecting him from Madara. Sasuke's purpose of being alive is to KILL Madara.
Itachi turned against Konoha on orders. He needed to gain Madara's trust so he would get to know all of Madara's secrets and plans. To accomplish that, he needed to become an Akatsuki member.
Maybe it's not direct orders of Konoha itself to kill the clan. Itachi's orders could be, was to find out all the secrets of Madara, find it out, and do whatever it takes.
Madara, of course not trusting Itachi at first, says to him to go and kill all the Uchiha's with him. But Itachi could've made an agreement to let Sasuke alive for some reason. While in Itachi's head the reason for Sasuke's life was to let him grow, be strong, and then to kill Madara.
Think about it, for Itachi to know if Sasuke was strong enough to kill Madara, was to see if Sasuke could kill HIM, as in Itachi, first. That's why he lied to Sasuke all the time to get the boy feel hate and let him be as strong as he can be.
Itachi thought that, one could kill Madara with the same MS. That's why the line of him, "You appear back in front of me when you have the same eyes as I have." Or something like that. (but you get the picture )But Sasuke did a good thing, learning to overcome the MS with regular Sharingan. (So there was a purpose for Orochimaru afteral except for being an total pedophile gay..)
Madara still has in plan to destroy Konoha, remember with all the collecting of the tailed-demons. Itachi tried to talk to Naruto, maybe even warn him for Madara and possibly Sasuke.. but Naruto was to stubborn to listen and wanted to kill the Older Uchiha right away. If Naruto heard him out, we would've known that Itachi wasn't the bad guy after all since then.
My theory, the Uchiha's evil thing that they could do, was to summon an tailed demon. If Madara could do it, so can another.
This may be go about something completely different then we are discussing if Madara's lying or not.. but think about the other stuff that's mentioned.. we're totally forgetting the previous stuff, because we're so worked up to figure out if Madara's telling the truth or not.