Well, there's Lovecraft, of course. He's been one of my favorite authors since I was 14.
Not "favorites" of mine, but certainly politically incorrect:
Jean Raspail's The Camp of the Saints is a work of undeniable power of imagination. It was published in the early 1970s in the US by Scribner, a publisher with a very good reputation, and with endorsements from respectable figures. It concerns the invasion of Europe by millions of immigrants from "Third World" countries. There's a description of one of the boats loaded with these folk copulating etc. The European countries are collapsing. The final image, as I recall, is of some white Frenchmen shooting at a swarm of the immigrants before they are overwhelmed. By most people's notions of racism, including mine, this is a racist book.
Alan Coren's The Collected Bulletins of Idi Amin, also from the early 1970s, reminds me of Twain. The author presents purported commentary releases from the Uganda dictator, written in a blustering "blackface" African-American mode for humorous effect. The first sentence, "Amin" referring to himself (as he usually is, in these "bulletins"): "Lotta people gonna be wonderin' about how de cornerstone o' Ugandan literature gettin' laid." From the back cover copy, supposedly from a Ugandan reviewer: "How we goin' to begin to describe wot goin' on inside de marvellous covers wid de superb photos o' de author, makin' it a must fo' de coffee-tables everywhere? As de maggernificent prose unfoldin', wid its smart sentences, many o' dese put into convenient paragraphs an' covered in top punctwation, we seein' not only a unbiased insight into de emergence o' de great Ugandan nation, we also privileged to watch de worl's foremost soul gittin' it all off o' his chest, settin' down de innermost thoughts in a vocabberlary wot runnin' into hunnerds, may wid up to two syllables." I take it the intention was to satirize the appalling Ugandan dictator as a pompous, pretentious fool. The "bulletins" were originally published in Punch, where I saw some in the series when I was a college undergraduate. It seemed funnier then. The pieces probably could not be published in a respectable magazine now.