I guess it is different for the new generation and the old generation. If you have experienced the history between Liverpool and United it must be something different to see them winning it than when you haven't. Must also be more infuriating when you are living in the Uk and working with Liverpool supporters or having some as friends or people you know. When you are insolated from that rivalry it all feels a bit more bearable.
However in the end of the day its only football and you should be able to distance yourself from it. I'd rather have more teams like Liverpool and the way in which they try to compete than like City, the sport would be alot better because of it. Their fans are unbearable, but I guess they can say the same thing about us when we were winning it for all these years. It goes both ways, we've had 20 years of dominance and gloating, we'll have to take the diffuclt times aswell, nice things don't last. Luckily the bad things don't last either.