Nobody knows what Ponting said, and it's a bit over the top to assume it was anything severe. The most likely thing is that he asked why it was given not out, and they got on the line with the third umpire and realised he'd given it not out because he wasn't sure it hit the bat, when it's not his prerogative to judge that, only whether or not it hit the ground.
You can criticise Ponting for speaking with the umpire if you like, but given that the decision that was given was blatantly wrong and after consulting further it was right, some blame has to be placed on the umpires for stuffing up in the first place. I very much doubt many captains would have said nothing in Ponting's place, and the fact that he did averted a pretty embrassing situation for the umpires, as they would have been giving the wrong decision based entirely on asking the wrong question.
Incidentally, Ponting has been reported by the match referee, so we'll see what happens.