In 1976, Andrew Britton wrong a long and careful vindication of the film, but his essay was not widely read. Britton noted how many of the reviewers didn't seem to have paid much attention to the film itself, given how many simple errors about the plot and character relationships filled their reviews. More famously (if academic press books by film scholars can qualify as "famous"), Britton's teacher and colleague Robin Wood devoted a chapter of Sexual Politics and Narrative Film
After watching Mandingo, I wanted to see if anybody had written about it more recently, especially within the film blogosphere, and that's when I discovered some real gems. I can't say I loved the film in the way some people have, but I certainly think the original critics who hated it missed the mark completely. It's a remarkable corrective to and comment on such things as Gone with the Wind, and some moments reminded me strongly of Gillo Pontecorvo's Burn!, particularly in the way both movies complicate the viewer's sympathies for the white protagonist.
But my purpose here is simply to point you toward some excellent online writings about the film: