The overarching point is well-taken, though. His openly shopping players has done harm (e.g., Ray, Rondo). If a guy's ego takes a shot from being dangled at every trade deadline, he's not going to play as well for you and, subsequently, you lose trade value.
Would that not spread to other guys, as well? You may not be the one on the chopping block at that given time, but I'm sure you'd realize you could be next at any given time. And I'm sure free agents are aware, as well.
From a fan's perspective, we like seeing him make aggressive moves. From a player's perspective, though, he would probably really suck to play for.