This video give multiple examples on illegal and legal ways to hit hard... showing that you don't have to launch with your helmet or completely back down to keep from being fined and suspended.

It also clearly states that just because there is NO helmet to helmet contact... you can still illegally hit a player using your shoulder pads or forearm to the head/chin such as the case with the Harrison hit on Massaquoi.

You can't tell me that a player of Harrison's skill level can't adjust to use his shoulder such as the positive examples provided in the NFL video to its players.