I think the other panther player involved in the tackle was what made it appear so bad. From memory in the replay petero had committed to the tackle before the other panthers player (sorry can't remember who it was and can't be bothered checking) made contact and started dragging him down. I really don't think it was an intentional high strike, though he maybe should have been more aware. But if the other player wasn't involved it wouldn't have been a high shot at all. Either way he probably deserves some time off for being careless, though Petero is far from a dirtbag who goes in for the high shots.
Then again maybe I'm biased, but considering his history probably not.