The biggest difference between all these sports that people are conveniently leaving out is that baseball and hockey are played in confined arenas. There is very little chance that violence on the playing field (or ice) will spill into the crowd (although there have been several exceptions). People forget that fighting in the NBA used to be not a very big deal at all. Guys would get in a fight and they would be suspended for 4 or 5 games. Then the "malice at the palace" happened and all bets were off.
Also, the last I checked, the NFL was a predominantly black sport, but when there is a fight during a game there, people aren't all up in arms over it. Usually if there is a fight in NFL games, guys get ejected from the current game and maybe receive a fine and that's it. Do people forget about the infamous Andre Johnson vs. Cortland Finnegan fight last year? That was a wild fight with haymakers being thrown all over the place. Both players were ejected and fined and that was it. There was no racial outrage over it. It happened and it was over.
Don't make something a racial issue when it isn't. It's a convenient excuse for people acting like godd*mn fools and getting away with it. People here would say the same damn thing if it was 20 white guys on the basketball court throwing sucker punches and stomping guys out when there were on the ground. There is no place for it on the basketball court.