The only diversity that matters is diversity of thought. For all the talk about diversity, it is always about the diversity of the superficial. Racial diversity and gender diversity rather than diversity of opinion and diversity of thought. This leads to the appearance of diversity without any actual diversity.
Sure, there is a case that people of different races have different perspectives on issues from their different background. Women probably experience life at least somewhat differently from men and vice versa (I would be very surprised if men and women experienced life in the exact same way). Blacks have different experience than whites, and so on. But that doesn't mean that having some black people in a group makes it diverse. You also need diverse opinions from the black community, as well as diverse opinions from every other community. No racial group has uniform ideas, and to think that you can capture the true diversity of humanity by checking racial boxes is naive.
Just as an illustration, if you take Thomas Sowell and Milton Freidmen (black and white), you will have less diversity of thought than if you had Milton Freidman and Bernie Sanders (white and white). Similarly, you have less diversity of thought if you had Jesse Jackson and Bernie Sanders (black and white) than if you had Jesse Jackson and Thomas Sowell (black and black). To have true diversity, you need to have people from all backgrounds of both race and politics, because that more fully captures the different perspectives of the issue.
It could be argued that because there are a minority of, say, conservative blacks, that this is a perspective that should not be included. But that looses the point about diversity. We should examine the perspectives of the unusual, because they are perspectives that the majority hasn't had the chance to examine. Just because the majority thinks something, doesn't make them right. In fact, we should give minority opinions extra examination, because we are most likely to suffer from confirmation bias in favor of the majority opinion.