Ponting was rightly pissed of as Pratt shouldn't really have been on the pitch.
Why?
Perfectly legal to have a sub fielder when a bowler is off getting treatment.
Pratt was on for Simon Jones, who's to say Jones would have missed the stumps? he had a very good arm.
It was Damian Martin on strike who called the run, Ponting didn't have the sense to either disagree or run hard, he set off later than Martin and got himself in trouble.
At no time is it acceptable for a player to act like that following a dismissal or any other time, Ponting was out of order and apologised afterwards.
Why?
Perfectly legal to have a sub fielder when a bowler is off getting treatment.