Both.
The easy one to explain is this: if they consciously or subconsciously are rejecting qualified minority applicants on the basis of race, that is clearly bad. I don't think I should have to explain why that is bad.
If they are completely unable to attract minority candidates, this also is a major problem. In general, there is a current broad movement in leadership training to try and incorporate more minority and female candidates into leadership in many fields (both academic and business). The reason for this is to diversify the idea vetting process being championed by leadership. Without a diverse leadership, ideas from the top end up being sort of homogenous as that group may simply end up being an echo chamber. Even worse, bad mistakes don't get caught (ie refer to the sexual harrassment crisis uber faced a few months ago and just now they are rectifying by appointing more women to the board of directors , or the nivea commercial from a few weeks that caught a lot of flak, or the huge blowback to the NFLs initially anemic response to disgusting cases of domestic abuse [ie ray rice] and etc). The fact of the matter is if you're running an organization and you are unable to recruit the best talent regardless of race and are recruiting a fairly homogenenous talent base particularly into leadership, you run the risk of missing out on truly great ideas as well as making gross missteps. A blind man cannot lead another blind man. Another way to think about it is that 40% of the US Fortune 500 companies were founded by people or children of people who did not come from this country (meaning they saw a niche that people here couldn't recognize was here all along and filled it). Think about the first person who suggested to nike to get into women's bras, or to consider monetizing American rap culture to sell shoes, and so on and so on. If your board room is all white men, these ideas may be passed up or not even conceived, but if you have diversity at the top, then these ideas are picked up and end up being huge success stories for your company. Thats not even probing the fact that this is a sign that the GOP is more or less ignoring massive demographic trends and are seeing Trumps win in the wrong way (as a sign of future growth, rather than the reality as a one off sort of event)