One of the earliest indications in the novel that Twain is satirizing racism and satirizing people who use the word "nigger" as a term of abuse involves the following comments by Huck's drunken, abusive, good-for-nothing father, called "Pap":
"And to see the cool way of that nigger—why, he wouldn't a give me the road if I hadn't shoved him out o' the way. I says to the people, why ain't this nigger put up at auction and sold?—that's what I want to know. And what do you reckon they said? Why, they said he couldn't be sold till he'd been in the State six months, and he hadn't been there that long yet. There, now—that's a specimen. They call that a govment that can't sell a free nigger till he's been in the State six months. Here's a govment that calls itself a govment, and lets on to be a govment, and thinks it is a govment, and yet's got to set stock-still for six whole months before it can take a hold of a prowling, thieving, infernal, white-shirted free nigger, and—"
Pap is speaking here, initially, of an educated black professor for whom Pap feels contempt. Clearly Pap's contemtuous attitudes are rooted in a sense of his own inferiority -- a sense of inferiority he would never admit. His hatred of black people is a way of over-compensating for his own failures in life. His sense of racial superiority is rooted in a sense of personal inferiority. He must find a whole class of people whom he can denigrate to make himself feel better about himself. Twain's presentation of Pap is just one of the many ways in this book that he makes it clear that he feels contempt for Pap's attitudes. Huck later finds, in Jim, a much better "father figure" than his own father.