What’s your point. “Going off” on rival fans is illegal. Allowing law abiding citizens to arm themselves for self defense will not legalize assault, attempted murder or murder.
How many stories have you read about where rival fans went after each other or one group beat up on another rival? So instead of the home team beating up on a visiting team fan like in LA a while back they or a bunch of them haul out their guns and start blasting each other. It’s not anything to do with arming for self defense; the story is about allowing people to carry in stadiums. You figure it out.