Tough situation, but then again - who among us would go to a new job and immediately start talking badly about coworkers and management after being on a sick leave for several months and while doing a pretty poor yourself? That's just not how you act.
The biggest thing that put me off Isaiah during his Celtics tenure was his contract talk. Not even legit max players talk about that. Then he goes to Cleveland where you COULD just be positive, say we gotta come together, I got Coach Lue's back, I'm here to win, I want the team to play well, it's on all of us... etc., pick your team cliche quote. Instead he's just constant negativity. What does he expect?