Atletico fans brandished "Aguero We Hope You Die" banners in a furious reaction to the striker's £38million move to Manchester City.
Atletico's president has backed the "outraged" supporters, saying he understands their attitude.
Cerezo said: "The fans have shown their disgust at him and I'm still asking myself what the hell we did to Aguero to make him treat us like this? Things could have been handled infinitely better.
"But the player had a buy-out clause, City paid it and there was next to nothing we could do.