@Lrx: I think much too much has been made of the lopsided nature of support for Hillary Clinton among African Americans in the Democratic primary. First, of course, it's important to keep in mind this is a primary contest, so support for one candidate over the other doesn't mean the other candidate wouldn't be supported in a general election.
Bernie Sanders certainly has a solid history of support for civil rights -- and his economic message is almost perfectly in line with the writings of MLK. It's unfortunate that Sanders didn't -- or couldn't afford to -- promote his early civil rights activism before the Super Tuesday primaries.
There are lots of time & place-specific historical/cultural explanations for African American voters -- especially in the South -- voting so solidly for Clinton over Sanders. First, of course, name recognition. And, as you note, the African American vote skews older & female -- two of Clinton's reliable constituencies. Clinton also spent a good deal of her adult life in the South (and even spoke with a southern accent while campaigning here). African Americans tend to be more religious than Americans generally, so Sanders' lack of overt religiosity was probably a factor. (Clinton pandered to the religious voters while campaigning here -- frequently referring to God, praying, etc.) Also, Clinton was a loyal member of Obama's administration, and Sanders has been a critic of some of Obama's policies (like most progressives) and some African American voters might take umbrage to that for understandable reasons.
Finally, this racial disparity among supporters virtually disappears as you go down the age scale (especially outside the South) so what appears to be a "racial" disparity is more likely a reflection of other factors.