Itachi never ever said anything like that. Itachi did leave Sasuke alive while making himself as the target of his hatred two time(after the massacre and when he met Sasuke a after orochimaru attack on konoha) but then again he was hiding konoha involvement. The only person so far who stated the possibility that you called is madara which is POV is to be taken lightly since he stated is desire to use Sasuke.
Are you mistaking here Itachi and Danzo ?
For Itachi it does matter that Sasuke was innocent because if his plan would have been successfull Sasuke would not have known of Konoha involvement in the massacre of the Uchiha. Itachi must have suspected that is attempt to trap Madara would be a failure so he left something to Naruto to stop Sasuke should he go against Konoha. He choose Naruto because Naruto feeling toward Sasuke are the more close to his own thus meaning Naruto would not decide to kill Sasuke unless he have to ( I think the lastest chapter prove that beyond doubt). But Itachi knew that if his little brother took the wrong path he had to be stopped even if he have to kill him to do so. That is what i believe.
Danzo did try to kill Sasuke because is existense could become a problem for Konoha but to think that Itachi would do the same is simply absurd. Itachi is not as cold hearted as Danzo.I d'ont believe he would kill somebody he love unless there is any other choice.
Sasuke might understand what is brother wanted but because he believe the same way you do that he was more important than Konoha peace in his brother eye that he could go and destroy konoha and make people suffer . Sure if Sasuke vengeance was only targetting Danzo and the elder Sasuke problem would only be after the actual shinobi system (and in a way it would be somehow noble) but since he said that he is gonna target all of konoha that change a lot. In the end Sasuke is not trying to make the world a better place to live he is just trying to satisfied is desire for vengeance but by doing so he disrespect his brother wish and if he do so it is because of that belief that he is more important to his brother.