What's iffy about white people calling out other white people? Isn't that what we want more of?

Also last time I checked, rapping was not an exclusive activity that only black people are allowed to participate in. In fact, in my admittedly anecdotal experience: black people are largely OK with whoever rapping, as long as they're not trying to mock rap or black people in the process. Don't do the art dirty and all are welcome, and all that