I think this is a major point, because even when you deal with really strong sports rivalries, it seems to be mostly play acting like they hate each other's tea

I think this is a major point, because even when you deal with really strong sports rivalries, it seems to be mostly play acting like they hate each other's teams. Actual hurt feelings are pretty rare expect for anger at particular events in a game (for example, bad ref call). With politics, it hits something much deeper in people and gets people to be side tracked for far longer, as well as possibly causing reductions in mood that translate to worse productivity.