My father may have heard Marais and Miranda in person, and I know they were an early influence on the direction he went with folk music. I remember asking him many years ago about their politics. It seems to me that his answer was to point out that the music they were singing was as much from the Afrikaaner tradition as from the Native traditions.
I think (pardon the spelling) there was an "Old Tante Kuba" song of theirs that he sang to us at bedtime. One of those "shut up and go to sleep or terrible things will happen if this lady babysits" kind of songs. ;-D