"Minstrelsy was certainly not celebrating black culture - it was a mocking and grotesque parody. Read this if you are in any doubt."

I did read this, what it says is a bit more nuanced than that (though of course Wikipedia isn't really to be treated as an authority). :

Blackface minstrelsy was the first distinctly American theatrical form. In the 1830s and 1840s, it was at the core of the rise of an American music industry, and for several decades it provided the lens through which white America saw black America. On the one hand, it had strong racist aspects; on the other, it afforded white Americans a singular and broad awareness of significant aspects of black-American culture.

The analogy Howard Jones made with "the present fashion for white youths to imitate the dress and mannerisms of black rap culture" is interesting - I suspect that future generations might well be likely to see that kind of thing as a "mocking and grotesque parody". And of course it might in time be done with precisely that intention.

And I suspect that for some black rap performers it may be a matter of adopting the mannerisms and dress on stage, in a way that has something in common with those black performers who in post Civil War days formed all-black minstrel shows, including black make up, as a way of getting a chance to perform.