Hockey is known for fighting. Baseball is seen as more of a pastoral sport, played on a sunny afternoon in June. For a game with such similarities to cricket, that is perhaps not such a surprising thing. But the major leagues have seen their fair share of brawls over the years.
Disco Demolition Night and 10-cent Beer Night were not included, since they were more riots than brawls, and even if you counted the former as a fight, it was between the players and fans, not the two teams.