They're not ignorant. They're racists.
It’s not racist, it’s just simple bigotry. You will find that the label bigot makes a far bigger mark on them than does racist because race hustlers have not only watered down their favorite label, most of the public discount it as a PC hammer rather than an actual accusation. Not only that, they are insulated against being called racist because everyone knows, blacks are genetically incapable of such.