As an impartial outsider, i have to say i had no idea that germany hated Bayern. Id always assumed you would have pride in your supposedly best team.
Though having said that Man Utd are arguably the most succesful team in England and everyone hates them apart from the considerable number of people living down south who "support" them because they win everything.
So i guess maybe i can see where theyre coming from. Has nothing to do with arrogance though. Man Utd arent automatically arrogant because they happen to win everything its just their manager is admittedly a genius but is flawed (and his lapdog second in command, the tool that is Mike Phelan) by his pathetic rants and inability to agree with a cast iron refeering decisions. In fact thats also why everyone hates their best player (and the 2nd best player in the world after messi), Ronaldo; his diving, loser antics and his insisitence that a.) he was fouled when he wasnt and b.) he is terribly injured as a result of said 'offence'.
Plus everyone has to have a team they like to hate especially the more succesful ones who have millions of pounds at their disposal to buy all the best players.
The rest is down to the fact you wont find a single manchester united supporter in manchester, they all support city because they dont 'glory hunt' like a lot of the population of outlying england!