How literate were the people (particularly the blacks) during MLK's movement?

I've been listening to a lot of his speeches and it is without a doubt clear that MLK was a very educated man. He knew a large vocabulary and was even very religiously knowledgeable as well as history. So I was wondering, as we assume today (I assume), that the black community (partly due to segregation probably) at the time weren't very educated, at least in terms of English vocabulary and other literate terms we hold onto well spoken and educated people, so how well were they able to relate to MLK?

It's funny because in contrast today, especially Trump, we're seeing the dumbing down of literacy which allowed Trump to relate to the common man so well today, because we as a people are generally more illiterate. Really quite interesting, but back to my main question is, were people, and specifically blacks really that literate in the 1960s? They had to be to an extent, otherwise they wouldn't be able to relate to him well?