I think I see where your coming from, but don't you think its more to do with the players/teams inability to cope with abuse from fans.
In the ideal world all players would be able to phase this out, as a example take the Ronaldo boo boys but then compare that with campbell who just went to pot. So i can understand it puts some people off.
You would think at this level the score line has more to do with what the players did wrong and what the home team did right then any other factor.
I think the loss in roma has to do with busy schedule, injured players, player being sent off, roma played better then us etc. I think the same can be said for roma too some degree. After 3 goals in such a short time, roma were shocked, united on a high, 7 goals were gonna come. You would think at half time they would of made some changes, and put up a fight. But no, man u scored another goal, players demoralized, game over.