The Las Palmas star was speaking on the Pescara man's alleged racial abuse at the hands of Cagliari fans in an Italian Serie A fixture on Sunday.
Reportedly the target of home fans, Muntari walked to the supporters to register his displeasure, but was then booked for dissent, after which he angrily walked off the pitch.
"I'm sad and I understand Sulley Muntari. Everyone knows that he is a wonderful guy and a winner," Boateng told Sky Sport.
"If he left the field, it's because something happened, and I have to say it shook me a little bit.
"It's difficult to explain how I feel. I'm sad and angry because those who are around close their eyes.
"When it happened to me, I also talked to the referee because their duty is not just to be there and be whistling.
"The referee doesn't just have to leave the field and give a warning [to the fans]. The referee should have more authority."
An irate Muntari lashed out at the referee after the match, saying: "The fans were wrong, but the referee had to act differently; not accuse me of causing trouble. I am the victim here.
"The referee does not just have to be on the field and whistle; he has to do it all, even feel these things and be an example."
In 2013, Boateng, then on the books of AC Milan together with Muntari, similarly walked off the pitch after being racially abused by fans during a friendly game with lower tier side Pro Patria.