"Why has Cash stood out for Hollywood from the ranks of country singers, most of whom mainstream popular culture dismisses and parodies as musically unsophisticated rednecks? Granted, Cash’s life story is filled with film-worthy drama: the Arkansas cotton farmer’s son who becomes a star, records with Elvis, but must overcome drug addiction, a marital break-up, and a series of personal tragedies to stay on top. But a major part of Cash’s appeal to the Left Coast and elite culture in general is political: almost alone among prominent country singers, Cash incorporated 1960s protest politics into his songs. That stance helped revive and sustain his career and brought disproportionate praise for his music"
(snip)
"By recording it ["Man in Black"], Cash embodied what the musical Left always sought: a 'man of the people' who is also politically correct. Cash’s song sounded all the themes of 1960s protest politics, including opposition to the Vietnam War."
http://www.city-journal.org/html/rev2006-01-13hh.html