why does the narrator stay and watch the burning of the black man?

One night in Macon, the narrator witnesses a gang of white assailants burning a black man alive. This traumatic event causes him to distance himself fully from his race and choose to pass as a white man. The narrator finds that he cannot turn away from the awful site. The burning of the man made him realize just how much of a coward he is. That man could have been him if he didn't lack the skin pigmentation to hide in.

"A great wave of humiliation and shame swept over me. Shame that I belonged to a race that could be so dealt with; and shame for my country, that it, the great example of democracy to the world, should be the only civilized, if not the only state on earth, where a human being would be burned alive." pg 137