So you should have!!!!
As to your point - half the fun of football is disliking opposition teams as well as supporting your own. Me personally I dislike half the premiership for one reason or another, and have soft spots for the the other half, but its all very fluid and largely depends on their relationship to United really as to how I feel about them.
As for the scenario you outline - can fully understand where he's coming from as what goods getting into Europe when your main rivals have bragging rights from winning the league... accepting relegation or even contemplating it's going too far though!