Holder is correct, but not in the sense he is thinking.
“Cowards” because we won’t sit with another “group”? (What he means is, of course, “whites won’t sit with blacks”....not the other way around or any other group.) I hardly call a natural inclination a show of “cowardice” in ANY fashion.
What he’s saying is a total misnomer; what he really wanted to say was “nation of RACISTS”, but for some reason he didn’t.
Sweeping generalizations such as those uttered by Holder are complete nonsense and only serve to further distance people of race from one another.