I assume you're using the full 7 game salary amount for dramatic effect even though we all know there's practically zero chance a "neutral" arbitrator will come in and just erase the entire ruling instead of compromising, especially given the ambiguity of the rule and the mandatory inclusion of "past history" no matter how old or irrelevant.
A neutral party like that isn't going to want to rewrite the rule book to remove the vagueness, which is what would be required, even though the NHL has already said the hit was arguably legal. Rules/disclaimers/etc are often written to give one party a distinct advantage in interpretation. Wilson and the Caps know this and even though they believe the hit was legal they know the NHL has the upper hand.
This has been stated MANY TIMES here but you keep ignoring that, instead choosing to insert your own narrative that the hit was clearly illegal based on the refused appeal. That's an inaccurate assumption.
Maybe most importantly, in asking for evidence I'm pointing to why your disdain for the "eye test" or other non-empirical forms of analysis is overly narrow. Interesting that you now value observation and subjectivity as evidence when you didn't before.
If the penalty was so obviously not boarding, as you have claimed, then why wouldn't a neutral arbitrator rule in Tom Wilson's favor completely? After all the arbitrator has his or own reputation to consider when handing down a judgment, so why would they decide to rule one way even though the visual evidence clearly points another way as you believe?
The arbitrator also wouldn't have to rewrite the rulebook, they could just say that Carlo wasn't defenseless at all. No change in rule necessary to come to that conclusion, just a different interpretation of the hit is needed.
I also think you are mischaracterizing what the NHL said about the legality of the hit. There's a wide gulf between "the hit was arguably legal" as you claim, and "there are elements of the hit that are legal" as the NHL claims. For instance, there were elements of Tom Wilson's hit on Oskar Sundqvist that led to a 14 game suspension that were legal: Tom Wilson didn't leave his feet, he didn't hit him into the boards violently, etc. That doesn't mean that hit was arguably legal.
And I don't have a disdain for the eye-test, but I don't trust it when it runs counter to objective data. For instance, if you said it feels hot outside but a thermometer says it's 30 degrees outside, I'd wager that your internal thermometer was way off.
There's no objective data to point out that this wasn't boarding, so I'm using a subjective view to say that every criteria was satisfied except maybe Carlo being defenseless. I've even admitted that I'm not sure I fully agree that he was defenseless. If the standard were reasonable doubt, I wouldn't vote to convict Wilson based on the evidence I have seen. I think there is a reasonable case to be made that it wasn't boarding. But I also think there is a reasonable case to be made that it is boarding. I think the NHL realized this, and because of this only levied a 7-game suspension when a more clear-cut boarding could have been 20+ games, given Wilson's history and Carlo's injury.
Reasonable doubt isn't the standard, and nor should it be in my opinion given that I think the NHL should err on the side of protecting the players.