Here’s the best I can come up with by way of a Clarke ∩ Obama intersection.
The only reference to racial conflict I can recall in Clarke’s work — and I recall it very dimly, across half a century, so may have it all wrong — is in his 1953 novel Childhood’s End. I guess I should put a SPOILER ALERT here.
A race of super-intelligent aliens arrive at late-20th-century Earth, with the purpose (revealed late in the book) of ushering the human race on to the next stage in its development. After arriving, they clean up the world’s trouble spots. One of them is South Africa, where, the narrator tells us, the black majority is cruelly persecuting the white minority.
That was a pretty bold prognostication to make in 1953.