As I've said before, there's a lot of things I'm not an expert on, including hockey, but I am 20 years law enforcement and deal with this sort of thing for a living, so I can at least make a claim to being an actual professional with regards to much of what is being debated.
Certainly a lot of different jurisdictions will have some different points of law, but a lot of the principles are usually pretty universal, especially around things like the appropriateness of any response and proportionality. For example, if I push you out of the way in a grocery store, you are not justified in returning to your car to get a firearm and coming back to shoot me, even if I started it..for two reasons. Firstly the response is out of all proportion to the harm or force meted out or caused to you, secondly, because once you've left or the confrontation is over, you are no longer protecting yourself when you go back, you don't have to go back; you were able to remove yourself from the situation and the harm was not continuing.
The incident here is not dissimilar in those regards, because you have a quite disproportionate response being meted out when it did not appear there was any continuing assault going on by the referee. Essentially there was no need for the reaction against the referee, other than perhaps some misguided sense of cameraderie.
In this instance, you have the benefit of having video footage of what transpired, although it isn't absolutely complete, you can't hear what might be being said by parties and you don't have full footage or multiple angles like you might do in a player safety decision.
It is readily apparent, that the referee in question is initially breaking up an altercation, directing or 'assisting' the player away from the scrum or melee and giving him directions to move away, demonstrated by his pointing away. There doesn't appear any intent to cause harm to the player from the outset; and intent is generally one of the key elements to establishing any criminal culpability.