> When I approached Anna to let her know that I did not feel comfortable rapping for a board member, she said “no problem” so quickly that it felt as if she knew she shouldn’t have made such a request.

That interaction might have something important the author experienced that we, as readers, can't visualise.

Also, a big part of this is that many times minorities don't want to reinforce a stereotype. There's a fine line to tread between one-off self-expression and the worry that the majority think that this is what you do all the time, or a label. I can see why the author doesn't want to be seen as "Derrius, the guy who raps."