City won 3-0 at Old Trafford and the home supporters later took out their frustrations on their legendary former boss, while David Moyes was also abused
Manuel Pellegrini's title-chasing side ran riot against their neighbours, with Edin Dzeko netting a brace and Yaya Toure rounding off the 3-0 rout late on.
And United fans later vented their anger at Ferguson, who hand-picked David Moyes to become his successor.
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In the first signs of open revolt at Old Trafford, stewards were also forced to guard the Stretford End's 'Chosen One' banner in case fuming fans attempted to tear it down.
Moyes later stoked the fans' ire by claiming United must "aspire" to reach City's level in the near future – despite beating them to the league title by 11 points last season.
He told reporters after the game: "I think we've played a very good side and it's the sort of standard and level we need to try and aspire to get ourselves to at this moment in time."
City, meanwhile, strengthened their own title bid with the victory, as they currently sit three points behind table-topping Chelsea with two games in hand.