While what Sasuke has done shouldn't be condoned, I really feel like he can't be blamed for it. Yes, he could have handled some things differently, such as his attempt on Karin and Sakura's lives, and I really dislike his attitude at times. However, he's a product of his environment. Remember, what we are is a combination of our nature and how we've been nurtured. He has a bit of the intense love and pride of the Uchiha and a very pragmatic attitude about getting things done, and all of the events of his life have combined with his personality to make him handle things in a very questionable manner.
But it's important to keep in mind that he hasn't had a chance to recover from everything in his life. It's been a slippery slope for him. He was pushed into a path of vengeance, by his own brother's encouragement, which led him to be involved with some very toxic people. As soon as he accomplished his goal, the proverbial rug was pulled straight out from under his feet, and his world came crashing down around him with the painful realization that his trauma originated from a very darker reason, which ended up destroying everyone around him. After that, things became even more chaotic for him.
All the pain from which he's suffered still underlies his actions, even with his change of heart, because he hasn't had a chance to distance himself from what's happened and entirely recover from it. His heart is in the right place, but he's going about things the wrong way, because he's so impassioned about getting things done the way he sees fit.
Like I've said in the thread about the movie, I don't agree with his methods and ideals, but it would be unfair to punish him for many things that he's done, just the same, because he was pushed to this point. It would be like blaming someone and/or expecting someone to do something, although they've been deprived of something by no fault of their own and are unable to do so. It would be the ultimate cruelty for him to be punished by the very people who symbolize what made him what he is today. Additionally, it would be bizarre for him to go back to the very people who ruined his life and act as though nothing happened. It would be too painful and would just perpetuate/excuse what they've done.
On that note, as I've reiterated, I don't agree with a lot of things that he's done. Naruto and Kakashi were damaged by the flawed Shinobi system, too, but they still have managed to lead less destructive lives and want to go about changing things in a less controversial way. But Sasuke's anger and pain are to be expected, nonetheless.