Mancini went onto the pitch to confront referee Peter Rasmussen after a controversial end to City's frustrating and damaging 2-2 Champions League draw with Ajax at the Etihad Stadium on Tuesday.
City striker Sergio Aguero had a goal ruled out for offside in the 88th minute and Mario Balotelli was denied an injury-time penalty as Rasmussen blew the final whistle.
Mancini also clashed with the cameraman who filmed him at close proximity as he walked across the pitch but later said he had only been telling him to stop recording.
First-team coach Platt said: "Why wouldn't the manager of a football club be frustrated? Why wouldn't we all be frustrated? Players are frustrated, supporters are frustrated, staff are frustrated.
"Robbie has gone onto the pitch and spoken to the referee. As he comes back, he turns around and has a camera in front of his face for 30 yards. He turns around and says, in English, that basically it is enough now. People then want to start talking about what has happened and almost exaggerating the incident."