What happened with Werek? He was a second round pick, and we traded him for another guy that was a second round pick (and evidently, a better player). That's a trade that looks like it will work out strongly in our favor. I understand your point, but that's not the best example.
Werek had attitude issues. My point is, you typically look to maximize value in a trade. You look for a team that has a need in their organizational depth, and are looking to move money.
If Miller could be packaged for a guy like Eric Staal (example) based on his potential as a player, but they are now hearing about off-ice issues and attitude problems, that could turn them off.
If the difference between an impact player as a return or a project lower-level player, is Vignault either opening his mouth or keeping it shut, then you have to keep it shut.
Or, forget trade value, if the difference is Miller pans out and becomes an impact player himself, but does elsewhere because he requsts out of the organization as a result of Vignault opening his mouth, then he needs to keep it shut.
There is more chance of something bad coming of this than something good.
You just don't throw guys under a bus in the media.
Tortorella threw Hagelin under the bus in the playoffs. He was fired. That isn't THE reason he was fired. But it was a part of it.
There are things a coach has control of and things he doesn't have control of. Flapping your mouth to the media about private matters is something you have control of.