It wasn't a dirty hit. It's just unfortunate that the hit took place where it did. Do you really think it was Chara's intent to drive his head into the stanchion? He has no history of dirty play and I don't think he'd intentionally do this.
I just saw that they said it was his C4, which is scary as hell. As the old saying goes "c4 and breathe no more". This could have been a real tragedy on the ice and shows how dangerous this game can be.
I think he meant to hurt him, which means Chara is guilty of one thing only, being a despicable human being. Unfortunatlely it was in the context of the game and dont think he should have been suspended either.