That's one perspective is: Another is that the player is getting paid to show up at time. Everything else is free flowing negotiation.
If the player feels unhappy(no matter if it's immature or completely legit), his right is to do what he seems fit to improve HIS situation without violating the standardized player contract negotiated by the NBPA and the NBA. He isn't getting paid to contribute to team chemistry. If the team is feeling that's the sole purpose of a player being on a team at a given time and the player isn't doing that, they can cut him(aka ask him not to come, while still honoring the contract)
Stephen Jackson on the Spurs is a good example for that.
In the end that action can backfire, as other teams may get more reluctant to trade for him, make offers in the future. Or it will just mean attention and teams will do a more thorough background check and coordinate better with the coach they have at the time they try to sign him.
I think that situation is more complex than the simplifications some posters try to derive from it. And from my perspective, I'm just curious how it will play out.
After all I prognosticated the exact same thing that's happening right now. Dennis's personality is one where he's very confident in his abilities, and as soon as he feels he deserves opportunities, he'll push for them.
It happened in his rookie season and the Hawks tried some disciplinary actions for him to find his place on the roster(The DNPs and D-League tours were supposed to humble him, as he was challenging the vets from the beginning)