The Premier League referee is under investigation by the police and the Football Association after the Blues launched a complaint accusing the 37-year-old of using "inappropriate language" when speaking to midfielder John Obi Mikel during Chelsea's 3-2 defeat to United on Sunday.
Ferguson came to the defence of the under-fire match official by claiming that that there is "no way" that Clattenburg is guilty of discriminating against Mikel.
Di Matteo responded by saying: "It's a free country and everybody can say what they want. He likes to talk about other clubs. We tend not to."
It has been reported that Clattenburg referred to Mikel as a "monkey" during the fierce league encounter.