In my opinion, black conservatives are so maligned by other people of their own race because there is nothing more "counter-cultural" than a black conservative. The Irish lived in this country for nearly 150 years before it became acceptable (but not common!) for Irish-Americans to admit that they voted for Republicans. Once the blue-collar union generation began to retire, and their children had grown up as professionals, then the inter-generational tension toned down quite a bit.
And if you dared to try you would immediately be branded a racist by those very people who talk about black leadership. Not only that, they would also fail to see any hypocrisy in it.