The Right loves unqualified candidates period, not just unqualified black ones. Many trace the genesis of this to Sarah Palin, but I think it actually goes back to Dan Quayle. Donald Trump, Christine O'Donnell, Todd Akin, Michele Bachmann and Rick Perry are not black.
And Dr. Carson is a horrible presidential candidate. Just the fact alone that he publicly said he wants to abolish Medicare and Medicaid shows a level of stupidity, both politically and as a matter of policy, which should automatically remove him from contention. The GOP "establishment" knows this is a general election deal breaker, but apparently the base is too lost in a Fox News fantasia to see reality.
Dan Quayle was a sitting US Senator for 8 years. He faced and won re-election in 1986, a good Dem year. The others were all elected officials except O'Donnell. Rick Perry was certainly qualified. He just had bad views on immigration
Vice President Quayle looked sooo "intelligent" when an elementary school student correctly spelled "potato" on the blackboard and Quayle corrected him and said he needed an "e" on the end for "potatoe." Pretty funny that an elementary school student could spell better than the Vice President. You can watch the video.
https://www.youtube.com/watch?v=Wdqbi66oNuI
As for Rick Perry, a presidential candidate who cannot remember three things is not qualified.
Dan Quayle is what happens when you allow affirmative action admits. No, I'm serious, he was admitted under a special affirmative action program for daddy knows the dean.