Answer: Douglass feels as if Plummer is a very cruel and miserable man.
Example: "Plummer was a miserable heavy drinker, a profane swearer, and a savage monster. He always went armed with a cowskin and a heavy cudgel. I have known him to severing the women's - heads so horribly, that even master would be enraged at his cruelty, and would threaten to whip him if he did not mind himself."