Interesting that you assume that the slaver is white. Jagger may have pictured him as white, but perhaps not. Not all slavers *were* white.
Many were black (and that number goes sky-high if you count the ones in africa who sold neighboring villagers to the european or muslim slavers.
And your final conclusion is a function of your initial assumption - who's keeping it a secret?
Jagger's dragging it all over the stage [pun intended]. And putting it on the charts - ain't no secret no mo.