Napoli defender Koulibaly was allegedly the subject of racist chants during the Boxing Day clash at San Siro, where he was sent off late in the 1-0 defeat to Inter.
Inter eventually clinched victory in stoppage time, but the post-match reaction was dominated by head coach Carlo Ancelotti's revelations that Napoli had asked for play to be suspended on three occasions, citing the abuse of Koulibaly as the reason.
Lega Serie A announced on Thursday that Inter's next two home games will be played behind closed doors, while the Curva Nord – a section reserved for the Nerazzurri's "ultras" – will be closed for an additional third fixture.
And Milan's mayor has now given his support to the temporary stadium ban, while agreeing with Italian Football Federation's (FIGC) call not to suspend Serie A.
"We'll call a meeting with Inter and AC Milan to avoid repeating these problems," Sala told reporters.
"I'd tend to agree [with the stadium closure], I understand they need to send a signal, but I don't know how to measure these things. I think a signal is the right thing though.
"Should the league be suspended? I don't think so, because objectively, in the face of such attitudes, there are also a lot of people going to the stadium with a positive attitude.
"So I don't think we need to suspend the league. It's not just a problem in Milan, everyone should take their own responsibility and mine is to talk with the clubs.
"This is something that goes against the spirit of our open city. I felt uncomfortable during the game and I wanted to leave, but I wanted to reflect on things."
Meanwhile, mayor Sala's Naples counterpart Luigi de Magistris believes Italy's football culture must change and blamed the officials for not stopping Wednesday's match.
"Unfortunately, racism in our country is advancing rather than receding," he told Radio Crc.
"The task of the state must be to curb it, but we also have government representatives who incite racial discrimination, divisions based on skin colour and geographical origin.
"Sport, on the other hand, should be preserved and an example of integration and equality beyond the colour of your skin.
"Football is increasingly disheartening from this point of view. On the one hand, it has bent to economic logic for too long, on the other, refereeing is sometimes absolutely unfair and shamefully unacceptable.
"If you get to a point where you won't stop a game, after repeated requests, it really means that you do not have the courage to impose what should be the rules of the sport."