Who ever said that "Fight Night" needs to describe a mass brawl though? It's hardly an official term from the dictionary, it can mean whatever people want it to.
As far as I'm concerned, any night that results in an assault taking place (as it did) and housemates being placed in separate rooms overnight classifies. That said, it's much more commonly referred to as Spitgate rather than Fight Night 2 so I don't see an issue either way.