Ferguson claimed earlier this week that Madrid had only signed Gabriel Heinze from the Red Devils in 2007 as a means of luring Cristiano Ronaldo to the Bernabeu.
Ferguson, 66, said in an interview with GQ Magazine: "I don't believe they were interested in Heinze - good player though he is. The end game was to get Ronaldo.
"What made it really obscene was that Madrid, as General Franco's club, had a history of being able to get whoever and whatever they wanted, before democracy came to Spain."
Calderon responded to those comments by saying in remarks reported by Marca on Thursday: "I'm not going to waste any time answering him, I admire his record, but he is getting old."