Ball Don’t Lie has a good comparison of just how good the Spurs’ method of addressing social issues has been, at least compared to the Mavericks’.
Colin Kaepernick’s silent protest was a way bring attention to an issue in a league that does not want you to have slightly different shoes.
The NBA, to Cuban’s credit, is different and allows for much more expression. A silent protest would be less effective than simply standing up and stating the issue on camera.
These are very different times and special message about equality was warranted. That the Spurs are the team that did it best is unsurprising.