Apples & oranges.
Each of those sports' cultures were established long ago, & I doubt that race played a major role in doing so. At one time ALL the major sports were all-white, & the acceptance of fights in baseball & hockey were the same . Basketball has not had a history of fighting- so when one happens, people are more appalled.
As its evolved, yes, basketball has become predominantly black, but what does that have to do with how fighting is perceived within the sport itself?
Since baseball is evolving & is becoming more Hispanic, does that now mean that fighting in baseball will be looked on as a "Latino" problem, rather than a baseball problem?
Yes, there are those who look at big black men brawling and see it as a race thing. But the original point was why is fighting more "accepted" in baseball & hockey, and less in basketball? That, IMO, has less to do with the race of the participants, than the culture of the sport.