My take is that while he probably had every intention of executing a clean hit, it was a direct hit straight to the head. The player didn't change position last instant or do anything outside of a regular play that you see in every battle in a corner, things some would say to rationalize a direct hit to the head.
I wasn't at the game, only have watched the footage linked above, to me I suspect Hlacar committed to the hit having anticipated where he thought the NB player would be, and was wrong and hit early. That's the risk when throwing yourself at a hit like a torpedo.
It's his second major in 3-4 games being too reckless. Sure he's big, it's not like we haven't seen big players before (Boris got a raw deal in his day!), its okay to be big, just don't be reckless or you'll draw even more penalties than just the "big guy" penalties.
I don't want to go as far as to say I don't 'Trust' him, but heading into the playoffs, anticipating he'll get at least a few game suspension, I wouldn't rush to insert him into the lineup right away when he becomes available. At least not as a regular 4th line shift.
As for a suspension, I expect at least 2-3, which in my opinion would be light, but for all we know it could be around 5 or even more.