Several days ago, philosopher Bill Vallicella asks, "what explains the Left's hatred of black conservatives?"
The Ben Carsons are simply a huge political and existential threat.Here are a few more explanations and thoughts from others:
Political: If the black vote were suddenly split, that would spell doom for Democrats.
Existential: The elite left needs to be needed. Ben Carson is a perfect example of someone who should but doesn't need the left.
They hate black conservatives the most because blacks are to them the ultimate left-wing argument against America. They are, even more so than indigenous populations, the group that has endured all that is wrong with our civilization, which they are endlessly trying to destroy and change. For a black person to then actually accept and champion elements of that civilization against them is the ultimate sickness within the black community. He's a traitor working with the "colonizers" and those keeping his own people down. He's equivalent in a way to a jew who is a Nazi, or the "house slave". That's why someone can call him "the most thoroughly despicable person" to run for president in modern times when he's neurosurgeon who's been helping to save people's lives for over 20 years.
Liberals see a man like Carson as an apostate, and to the faithful, an apostate is far worse than a mere infidel. You've seen the same attitude at work in the university, where conservative professors are held in greater contempt than, say, conservative lawyers. Like conservative Blacks, conservative professors are seen as traitors to the tribe, apostates. Traitors are always dealt with more harshly than mere enemies.
Bill, the "race is a social construct" doublethink is one of the hardest self-delusions of the Left for a rational person to get his head around. On its face it seems an obvious absurdity to build so much of one's ideology, and to expend so much effort and political capital, on something that, according to one's own dogma, has no reality.
The only way it can even begin to make sense is if race is superficially real, but only "skin deep". In other words: yes, there are ancient human subpopulations that differ in their pigmentation -- but these variations in skin color absolutely must not be imagined to correlate, even statistically, with any other human qualities (unless, of course, the comparison with whites is a positive one). In this way race becomes just "real" enough for right-wing bigots to pick out their victims, and for liberals to succor these victims as an oppressed class.
So: to be a member of the victim class, but then to turn your back on your saviors on the virtuous Left and associate with your oppressor, is not only to betray your race, but to reject the Good. (And to insult the good people of the Left -- but I repeat myself.)
See also the smearing of Ben Carson.
And don't forget Herman Cain.