This episode is really not as bad as it should be considering that it says nothing of particular value, and uses the "fight to the death in an alien arena" motif again. Rather than making things worse as you'd expect, Lincoln helps the episode slightly, though it feels somewhat cheap to trot him out simply to commune with Kirk and then fight to the death.
As to the the reviewer claiming that Lincoln says "the N-word," he says "Negress" which is probably not the "N word" most people would ever think of. It's still not something you would ever call a black woman today, but is more of an antique term than the common, intentional, ugly racial slur that "the N word" usually refers to.
Since Lincoln is so iconic, you'd expect him to do or say something useful or profound. Instead he simply lends his icon to the Enterprise for a while, he says some things about fighting if a fight is forced upon you, and crawls around on the rocks and bushes for a while.
Could've been a better episode. I call foul for calling up historical characters and then putting them in a World Wrestling Federation match. Is that the best they could do?