Yes, everyone loves upsets, but people here have always loved to see Rupp lose. They loved it when he kept losing to Lagat, even though Lagat was always the favorite, at least back in they day. They hate him either because they're convinced he's doping (a good reason), because they're envious of his resources, or because they simply don't like awkward-looking people. I suspect the third is most likely. It's the whole "have a beer with..." thing.
Centro is also part of NOP, which covers reasons 1 and 2, yet I don't see anywhere near the same sort of hostility towards him. Certainly some do dislike him, but it's not like Rupp. I suspect half of the posters on here are dancing in front of their computers. I don't think they would be doing that so gleefully if Manzano or Andrews won instead.
The Johnsons' also seem to dislike him more than other NOPers, alluding constantly to the fact that he isn't any more talented than the other runners (took forever to break 4, True was better as a part time runner, etc...), and doing it in a way that implies that there must be 'something else' giving him that edge. For them, I think they must have inside info or stories from people they trust that they can't really publish but that color their view of him. Maybe they just hate all nerds, but they seem professional enough for that not to interfere with their judgments, or so I hope.
I'm surprised Rupp lost this race, even if it was slow. He really is much better at the 10K. He beat True so easily on Thursday, yet almost missed the team here. This style of race didn't really suit him, but it's really hard to see him medaling at 5K if he can barely make his own team under any circumstances.
I think Rupp is doping; there's way too much smoke in the allegations for there not to be a fire. However, I feel that most top athletes are probably doping (at least all the NOPers) and that anti-Rupp sentiment stems from the fact that he comes across as a nerd and people hate nerds.