Mourinho was speaking on the eve of his team's home clash against Bournemouth, but the pre-match build-up centred on an alleged fracas between United and City players after the visitors left Old Trafford 2-1 winners on Sunday.
David Silva and Nicolas Otamendi lifted City as Pep Guardiola's runaway Premier League leaders moved 11 points clear atop the table, though news quickly emerged about an incident in the tunnel post-match, reports suggesting Mourinho and several members of United's team and coaching staff took offence to apparently disrespectful celebrations.
Mourinho and Guardiola were careful when discussing the scuffle on Tuesday, and the United boss become visibly irritated when pressed on the matter by reporters at Carrington Training Centre.
With the Football Association (FA) contacting United and City for their versions of events, Mourinho was asked if he expected anyone from the Red Devils to be punished and the Portuguese tactician quipped: "Why? I think you work for another club and not for the press."
The attention then turned to United forward Romelu Lukaku amid claims he could face punishment for throwing a water bottle during the scuffle at Old Trafford.
"Accuse? Prove? Show evidence and punish him," Mourinho said. Asked if he thought his United players behaved, he added: "I know. I am not confident — I know."
That pushed Mourinho over the edge as the 54-year-old left the news conference with a parting shot at reporters.
"You don't like Bournemouth, eh? You don't respect them," Mourinho said as he walked out of the room.
"You don't think they are a team capable to come to Old Trafford and do well. No respect for Eddie Howe. No respect for their players."