The striker had a heated discussion with referee Luca Banti following the 2-1 loss to Napoli which has seen him suspended for three games as a result.
"What happened after the final whistle counts for nothing," Tassotti told Milan Channel. "The match was over and you cannot change anything then.
"I was there at the meeting with the referees where the captains were also there and the outcome was that the players have to be more educated when they come to confronting the referee.
"You can ask them a question, but you cannot go too far and in this case Mario probably overstepped the mark and was in the wrong.
"I don't know exactly what happened because I had headed down to the dressing room. We have to accept what happened and take the outcome as it stands."