There's nothing good about electing a group of incompetent people to office because they happen to visually represent the ethnic makeup of the country. There is much good about electing good and competent people regardless of their ethnic makeup. If we could elect 100 wise and capable Senators, skilled in legislating and negotiation, who were all black, the very stupidest complaint I could devise would be that they don't look like the rest of the country.
I guess fundamentally that's my issue here. I suppose it'd be ideal if we could get a perfectly proportioned legislature that perfectly represented the whole of American diversity. But if I have to choose between diversity and competence, diversity loses, and should lose, without a moment's thought. I think it's wrong to see racial diversity as a good to be pursued. It's good if it happens naturally. It's necessarily prejudicial and wrong if it's sought out, because it involves saying "we want more of Race A and less of Race B."