Disclaimer: I am not trolling, I am an autistic person who doesn’t understand so many social nuances. Also I am from New Hampshire (97% white), so I just don’t have any close African-American friends that I am willing to risk asking such a loaded question.
You build up knowledge over time by paying attention to how the culture that it is tied to responds, since most racist stuff doesn’t make logical sense.
For an example of it being complicated, the Florida Seminoles college football team is fine because the school has coordinated with the tribe. I don’t know of any other professional or college sports team that does so, and any that don’t are exploiting Native American culture and most likely using racist stereotypes as part of their team ‘spirit’.