Eh, I don't care about this at all.
Firstly, I doubt this happened this year. It certainly didn't happen since Rondo injured himself, and it's unlikely it happened in the immediate time before, when the Celtics were on that losing streak, since that's when these type of stories leak out. Nor did it leak when the Celtics went on a winning streak after Rondo got injured, and the prevailing meme was the Celtics are better without Rondo. It's likely a couple years old if it happened at all. My guess would be the 2010-2011 season, since the Celtics made a real push to trade Rondo the following off-season.
Secondly, this clearly didn't come from the Celtics. It's just the Clippers, or some other team, trying to have fun and stir the waters.
Thirdly, it's no secret that Rondo doesn't always control his emotions successfully. But it's in competitive environments when his adrenaline is flowing. It's that same adrenaline rush that let's him play on a torn ACL, or win a game with one arm, or defend LeBron from half-court, or turn superhuman in the playoffs. So once every couple of months he does something stupid. He's a smart dude, and I bet he realizes it afterwards, unlike DeMarcus Cousins.
Finally, he may get heated on the court or in the locker room, but he's never in a bit of trouble off the court. You don't see him partying after a loss, and if you did, he'd have a Shirley Temple in his hand. You certainly don't hear about him getting into bar fights, gun fights, or DUI. Instead you hear about him going to Paris, or interning at a fashion magazine, or playing Connect 4. Occasionally he's petulant, and maybe a know-it-all, but he's a great basketball player who's incredibly competitive on a team-friendly contract who you don't have to worry about at 2am on a Saturday night. He's not perfect, but as we see with Aaron Hernandez, you could do a lot worse.