The Rossoneri striker became the target of the visiting support when he was shown a yellow card for a late tackle in the latter stages of the first half and his coach believes the intentions of the guilty parties are an indictment on the country.
"My thoughts on the match being suspended for racist chanting? In Italy we have this mentality, a culture that is a little backwards because you should come to the stadium only to watch good football matches," he told Sky Sport Italia.
"We had two games in hand, now we only have one left and we will win at Siena. We risked [losing the match] in second half, playing with 10 men at the end and we kept a draw at home.
"I'm sorry that we've made our fans wait another week, but we know our fate is in our own hands. We'll be playing against a team who are already relegated, but we won't be receiving any gifts."
Allegri then attacked the decision to send off Sulley Muntari, but nonetheless remained confident in his side's ability to secure Serie A's third and final Champions League spot against relegated Siena next week.
"These things should not happen, it would have been another game 11 vs 11 and I could have made a few more changes [prior to the red card]. However, we have an advantage over Fiorentina, but we must win at Siena," he added.
"El Shaarawy? He must vary more in his play because Serie A has begun to work him out and above all he must not have to live with the obsession of scoring a goal.
"This team has 69 points after a disastrous start, so we must remain focused and not be fearful. We must approach Siena calmly."
Meanwhile, Milan vice-president Adriano Galliani confirmed that centre-back duo Cristian Zapata - currently on loan from Villarreal - and Philippe Mexes will stay on as the club's first-choice defensive pairing next season.
He told reporters: "Zapata and Mexes are a good defensive pair, and they will be here next season. I am confident we are going to play in the Champions League."