Since ancient times, the study of rhetoric has always included the level of ethics. The so-called rhetoric is the skill, skill or art of using language to persuade others effectively. The ethical value of rhetoric as a public discourse includes good motivation, goodwill to others and the truth of the content of the discourse. If you leave or turn your back on such ethical values, speech skills will become a kind of improper rhetoric, a means that can be used to achieve an end, an improper sophistry or clever speech.
The central topic of this passage is the ethical value of rhetoric.