They are the equivalent Ferrari F1 Team in football, and as such, there's much to dislike:
Arrogant fans (the plastics)
Arrogant managers over the years - Docherty, Fergie, Van Gaal, and now Jose to name a few.
Arrogant club persona
Arrogant players - Keane, Keane and Keane!
Expect and get helping hands form referees and the system in general - e.g. Fergie time, many dodgy pens, allowed to miss the FA Cup to promote pathetic, grandiose flop the Club World Cup.
Red
Won loads
Massive sense of entitlement in club and fans.
Think they are bigger and more special than everyone else and even the game itself sometimes; think the game relies on their presence and so will die if they disappeared.
Their years in the doldrums after the Fergie era has dulled my dislike though - but I am not feeling sorry for them yet!