'Men In Black' is a finished song.
Author Adrian Grant heard a finished version of it (in 1990), and he later shared his thoughts about it to several fanzines.
He also stated (back then) that 'Men In Black' was similar to Paul McCartney's 'The Man' song (1983).
Here is what Adrian Grant also stated about the 'Men In Black' song more recently:
"…Michael then asked if I would like to hear a track from the new album, which I'm led to believe no one else had heard at them time. He played me 'Men In Black', which was funky and loud, but ultimately never made it onto the final track listing [of the 'Dangerous' album]. I stood by his side nodding my head to the beat, as Michael sat at his mix desk pushing various buttons…" (Adrian Grant, Interview to Brice Najar)
Also, certain press reports (from back in the day) wrote that 'Men In Black' was planned as one of the singles from the upcoming 'Dangerous' album, which clearly implies that the song was finished but it was replaced (in the final track list) at the last minute.