Just adding my two cents worth...
Sumo fans are not necessarily different or more genteel than other fans
(remember the uproar recently about the actions of the Nagoya crowd?).
However, we must look at the context of the two examples that Joe has
provided.
The China jungyo/koen was a smaller crowd, watching something promoted as a
cultural performance as much as a sporting contest. Also, there was not
really a sense of nationalism that went along with it, as the whole thing is
nationalised as a 'Japanese' event (even though there are Mongolians,
Chinese, Brazilians etc involved). So, the crowd came to observe rather than
support one side or the other.