Probably true but I'd bet that the black population in America was just as peeved as with this new casting choice. The fact is that in the early sixties there were absolutely no nationwide (or powerful local) outlets for the collective black voice. I suspect that it is this restricted access to public media that is at the root of the perceived absence of discontent.
Actually, the myth that all good things done in Egypt were done by people with black skin did not exist back then. I think it was the early 1970’s when blacks started saying that all important people in history were secretly negroes. Jesus was black. Socrates was black. Beethoven was black. It goes on and on. When Elizabeth Taylor starred in “Cleopatra” this sort of thinking had not yet been dreamed up.