Well, the premise of the post is that there must be some criteria that one must meet to be qualified as a bona fide "black", though I can't recall ever having read "the manual". Perhaps it was lost in the mail.
There are, however, black people who embrace certain precepts of the more conservative agenda, and still others who think they do because (like their white counterparts, of course) they are not fully apprised of exactly what the ideology entails. They, like everyone else, arrive at their political perspective by the sum of their own personal experiences.
Therefore if someone like Cain believes his personal success is the fruit of his own making ("I got mine, get yours" mentality), then it's highly possible that this person would believe (as Cain does) that one's failure is solely of one's own fault. His right to think so. OUR right to disagree.
Cain, whatever he is or isn't, embraces ideology that is counter to that which I (and many others) value. He demonstrates a lack of understanding of certain complexities - difficulties with which many have to deal. He (and his counterparts) show an unfortunate brevity of compassion, imo (electrify the fences, indeed).
Black, white, whatever, Cain would not be an option.