Okay so I'm kind of puzzled by this one.
The authors randomly assign black male patients to black or white male doctors, and find that the patients are more likely to take up preventative treatment after meeting with a same-race doctor. They argue that this means that "diversity" is important among doctors.
The glaring hole I see in this argument is that the decisions (in this case) belong to the patients. So the (black) patients are only doing it if the doctor is black.
Does that mean that diversity is important? Only in so much as the patients are unwilling to listen to the equally good advice given by the white doctors. And so the story seems to go "black patients are racially biased, so it's important to have black doctors in order to satisfy their racism." How is that not the story they are telling here?