Just reposting this explanation/background for this type of stuff at 9ers games from the other 9ers friend where this vid was first posted, if anyone is curious.
It's true that we have know way of knowing if thats the story in this video, but having been to a ton of 9ers games since the below transition happened, well, umm, I have yet to see it NOT be the story...
Due to California's gang injunction and three strike laws in the 90s and early 2Ks prison-gang populations boomed and 5-10 years out upon release those prison gangs ended up jumping the walls and becoming street gangs (the state of CA basically created the problem it was trying to prevent).
This is only relevent to the 9ers because one of the -if not the- largest gangs to migrate out of prisons was the Nortenos ("Northeners"; a loosly affiliated network of bloods), who ended up adopting the 9ers because of the color of their jerseys. With that transition in the mid-2Ks the reputation of 9ers fans transitioned from wine sipping effettes to thugs.
As a result you end up seeing stuff like you saw in that video: A bunch of 9ers fans yelling stop and trying to break up fights while guys who were hardened and criminalized through doing prison time due to draconian sentencing (and are 9ers fans because they rep Northern California and 9ers jerseys match their gang affiliation and Raiders' jerseys don't) are starting a bunch of fights between each other and with random others.