^Yeah. It happens when you go on a quest for revenge and give up everything, when you don't even know the truth and give up those 8 years of your loving brother in your mind for something that happened in one night, and don't think it's suspicious but act upon your emotions entirely and throw common sense out the window and don't try to find out if there's something more to the story.
Poor Sasuke. Don't really blame him for the taking revenge part though. Itachi knew that he'd do it and wanted him to, because he knew that it would benefit his little nii-san in the end. But everything that occurs after Itachi's death can be considered Sasuke's fault.