Allegri made the plea after Kevin-Prince Boateng was subjected to prejudiced chants in his sideÃ¢â‚¬â„¢s match against Pro Patria at Stadio Carlo Speroni.
The encounter was abandoned midway through the first half when Rossoneri players decided to leave the pitch, after the 25-year-old kicked the ball toward the home fansÃ¢â‚¬â„¢ stands after receiving abuse.
Ã¢â‚¬Å“We are disappointed and saddened by what has happened,Ã¢â‚¬Â Allegri, 45, told reporters.
Ã¢â‚¬Å“Milan play for the right to respect all players. We need to stop these uncivilised gestures. We are sorry for all the other fans who came here for a beautiful day of sport.
Ã¢â‚¬Å“We promise to return, and we are sorry for the club and players of Pro Patria, but we could not make any other decision. I hope it can be an important signal.Ã¢â‚¬Â
Manchester City captain Vincent Kompany also commented on the incident, and called for stricter punishment for the offenders.
Ã¢â‚¬Å“Act of racism against Boateng during MilanÃ¢â‚¬â„¢s friendly. How about becoming extremely intolerant towards racist idiots? They need to be told,Ã¢â‚¬Â the 26-year-old wrote on Twitter.
Ã¢â‚¬Å“I can only salute MilanÃ¢â‚¬â„¢s decision to leave the pitch. Also noted that the majority of the fans were completely supportive of the players,Ã¢â‚¬Â he said.