You can't just leave out legality from the equation. There are rules for a reason.
There's a line between doing something ruthless and doing something that is a textbook violation that won't get prosecuted (because it's affect is going to lead to no action).
If the NHL and PA wanted it to get rid of teams threatening to waive a player if they don't accept a trade (something plenty of other teams have done), they'd do so. They don't want to. There's nothing you can do about an agent threatening a player to violate their contract. Freedom of speech applies and also the way contract law works there's no way they could ever enforce a threat as a breach of the contract.
That's where you get the difference between ruthless (mean but legitimately fair) and unethical (a violation of the rules that there's no real way to punish).
Legal doesn't equal ethical and vice versa. There are things that're illegal but not unethical, and there are things that're unethical yet not illegal. Your original post made it seem like you were quite concerned with the ethics of it all.
While the Rangers waiving Goodrow was well within the rules, I don't think you'll find many unbiased people saying it was ethical. But that's just buisness, way she goes sometimes.
While Trouba's camp threatened to do something against the CBA, the simple threat of it is just as legal as placing Goodrow on waivers.
Now if Trouba did indeed get traded and follow through on his threat, you seem to think that would go unpunished. Yet if Trouba is as overpaid as some people think, he surely wouldn't get an $8m AAV again. Walking away from that money is certainly a form of punishment.
Let's say the Rangers pay to get rid of him (like Columbus did by attaching a 2nd to Laine), and Trouba and the new team mutually agree to terminate his contract, nothing against the CBA happened because mutual terminations are allowed.
Now if the acquiring team legitimately wanted Trouba to play for them and he didn't, they would absolutely have avenues to go down to force his hand. The Islanders tolled Nabokov's contract when he refused to report after being claimed off waivers from Detroit. So Trouba could very well be stuck on a new team indefinitely if that's the route the team wanted to go.