Nasri hasn´t really said anything at all through all this. I find it difficult to understand why there seem to be so many that are upset with him.
From the beginning he was just a guy who seemingly wasn´t happy with the proposed contract from the club. That much was confirmed. Not by Nasri though, but by the manager. Nasri kept quit. Then he seems to have decided it is better for him to ply his trade elsewhere. We really don´t know, because Nasri himself has kept very quiet and only conducted his business with the club, not through the media.
IMO he has done nothing wrong. Can´t even blame him for thinking it would be a good career move to move to one of the Mancunian clubs. He is most probably right.