[I]t may make sense to view Jackson as a reverse Al Jolson, the white entertainer who made it big in blackface in 1920s Hollywood.
To which I can only reply: no, it doesn't.
Granted, Jolson's contemporaries considered his blackface performances to be of an anti-racist sort (especially since Jolson was Jewish and so only a marginally white person himself) and he's credited with popularizing jazz and blues within white America. But let's not forget that blackface rarely encouraged anything more than a superficial relationship with its material - that it was a hyperbolic performance that plays up the cool, the illicit, and the sexual aspects of an imagined black community for the amusement of a white audience. And that Jolson's blackface - by virtue of being so clearly theatrical - also served to establish his claim to whiteness by way of contrast: the falsity of his blackface made real and authentic his 'whiteface'. (And while it might have opened doors for black musicians to cross over into white spaces, it also prescribed the stereotype that they were expected to fit.)
It would be difficult, or impossible, to suggest that MJ's whiteface had that sort of reciprocal effect (especially since most people think it delegitimized his blackness) or that he performed whiteness for a black audience so as to make it something they could control and consume. It's difficult to suggest that he had any explicit politics at all, much less to suggest that he thought he was doing whiteface.
A friend told me that it's pointless to keep talking about the "real" Michael Jackson and to impute what his body or his behavior "means", as if it isn't already overdetermined. (To paraphrase Foucault, he resembled his crime before he committed it. If he commited it at all.) All that we really have, she said, is his music. That might be a tad oversimplified, but it's preferable to his unproblematized reimagining as queer revolutionary and anti-racist icon.