I have not heard the tape
But I have heard people say Martin Luther Coon
It did not appear to be a slip of the tongue
It doesn't mean that it wasn't.
By the way, until this discussion I had never heard of the "Martin Luther Coon" slur. So if I, at 55 years of age, have never even heard of it, isn't possible that this guy, who is probably twenty years my junior, had never heard of it either and that maybe, just maybe, it was an honest slip? Is there any possibility in your mind that this might be the case?