I agree with Alen. They handed the game to Milan with that sub. Not to mention Empoli's finishing was poor. They should have been leading at HT. The loss was tough, but they didn't do themselves any favours.
As for Inter, how many pk's have they received this season, both for and against, compared to the rest of serie a?
Also, off the top of my head: Parma, Siena, Empoli, Catania, Reggina were all games where they scored from debatable calls. I know I'm missing a few though...