David is correct, many Mancunians support United - although I might take issue with him saying there are more United than City actually in
He is also correct that Manchester United have historically had very high attendances (usually at Maine Road actually), although until relatively recently City were always higher, and have the higher record attendance of the two.
It is interesting that of those who don't attend games, more of them will profess an allegiance to United. In my father's family, he and his Dad were City fans, and went to all the games. His brothers were United fans and didn't. I suspect that might be mirrored in a lot of families.
Success breeds support I'm afraid. I don't have a problem with people supporting United provided there is a connection, it is the ones who simply decide to "support" them because they are top of the league who get on my wick.
Actually, I compare these people to Nazis. They have the same method of thinking. Put them in 1930's Germany and they'd have said, "That Hitler's doing really well, I'm going to support him".
She's as nervous as a very small nun at a penguin shoot.