I might get some flak for this from fanboys, but whatever.
After Sasuke's battle with Itachi, he learned the truth behind the slaughter of the Uchiha Clan: They had been plotting a seperatist movement, and possibly outright treason, against the rest of Konoha. For this reason, Itachi was ordered to wipe out the entire clan to keep the village from splitting into two, because hey, this guy really loves his village. So far so good.
But, when he learns this, Sasuke flips a complete 180 on the ambitions of his beloved brother, and makes it his sole purpose to wipe out one of the only things in the world that was precious to his freshly deceased sibling.
Apparently the one ability the Sharingan can't give you is logic.
What do you think?
Don't let my avatar fool you. I may like Sasuke, but I'm not a fanboy. That being said, let my point a couple of flaws in your argument if you please.
It's the bolded part that makes little sense, which everyone so far has completely neglected. Sasuke never made a "180" on the ambitions of his brother. In fact, Sasuke never cared about the ambitions for Itachi in the first place, so I'm a little confused as to when or to what did Sasuke make a complete turn to.
Sasuke's ambition as far as we know has always been to restore his clan; that's it. Itachi's ambition for Sasuke (which, like you said, was the sake of the whole village), is a complete contradiction to what Sasuke wants (which is the sake of his clan). In order for Sasuke to make a "180", he would have to first align his will with that of Itachi's (that is, desiring peace within the whole of Konoha), and then cease to align his will (desiring the destruction of Konoha): hence the "180".
Your statement would make sense if the above were true, but it's not. Sasuke always wanted to restore his clan, whereas Itachi wanted the clan gone because of the friction they caused with the rest of the village. So no, I'm sorry to say, but Sasuke never made a "180" in the first place.
He did, however, decide to add on to the list of people to kill to restore his clan. After he learned about the truth of Itachi, he still wanted to "purify" his clan by destroying the perpetrators of his clan's destruction. Itachi was the beginning, not the end of the people responsible for causing he clan's destruction. Itachi was simply an instrument, now he wants to go after the orchestrators, if you will.
That actually makes logical sense. We may not agree that was Sasuke is doing is moral, but it makes sense that Sasuke seek to do this. If anything here lacks logic, it's your erroneous claim that Sasuke made an imaginary "180" to his brother's will which he never sought to fulfill in the first place.