I don't hate Man Utd and I don't believe people really do. It's just that over recent years they have had a lot of sucess and done it in a way which was very classy. Problem is that when things don't go there way, they get a bit snooty about it and blame the ref etc... instead of taking the defeat on the chin.
Also a lot of Man Utd fans have huge expectations and for a long time have had a bit of monoply (well, during Premier League) and cause of that people were no doubt bored of seeing Man Utd get the sucess and LUCKY with having so many great players come through youth at same time.
I don't hate Man Utd, but I damn sure well find it funny when they loss.
Liverpool... NOW THAT'S a team I hate....