In the introduction of "Corn-pone Opinions," Twain describes Jerry, a "delightful young black man—a slave—" and then goes on to introduce verbal irony in claiming "I believed he was the greatest orator in the United States and would some day be heard from." Twain was well aware of the racism and systemic discrimination that would prevent men like Jerry from being "heard from" in America.
In writing this essay, Twain is calling out his readers for their conformist behavior. His assertion "broadly speaking, there are none but corn-pone opinions" is another use of verbal irony because Twain himself is offering a decidedly nonconformist opinion in pointing out why people behave as if it is necessary to conform to prosper in life.
A third utilization of verbal irony occurs when Twain avers "self-approval is acquired mainly from the approval of other people." This observation is oxymoronic and underpins Twain's overall argument in the essay. He is calling for his audience to become independent thinkers and actually reject the phenomenon of valuing one's thinking by how closely it parallels that of the majority.