A Celtics fan threw a Dasani bottle at Kyrie Irving the other night. He was arrested. He should be arrested. First, he should be thrown out, and maybe lose his privileges to ever be back. Arenas, teams, and leagues have the right to enforce decorum in that way. Their house, their rules. The article lists other bad behaviors by fans, some of which warrant arrest, but all of which is in the purview of the people throwing this party to exclude customers who aren't getting with the program.
But it is not automatically racism just because the target was black. Irving gets it partly right in terms of history and entertainment, yet I think he misses the part that tomato-throwing was largely white-on-white crime for hundreds of years, but still weaves it into the modern racism narrative.
It could be racist, of course. If we let the accused talk long enough he might say enough to convince us that he would not have done this to Gordon Hayward, who also used to play for the Celtics. (I admit even that is not a perfect analogy.) However...the NBA is mostly black. Guys who used to play for your team but are now coming back and might defeat you are going to be disproportionately black. It's one of the things that African-Americans aren't used to, being so dominant in an area that they are the default, the generic NBA player. I will note in passing that there is considerable resistance to the idea that they are in one of those areas where whatever societal prejudices might be in play, they ain't in their neighborhood.
This is part of the slow build of resentment that is not based on evidence. Because of confirmation bias, people who already convinced this is all racist will take this instance as evidence. But it isn't. Yet it will be added to the fuel.
Update: The arrested fan was wearing a Garnett jersey.