The word "should" is a modal verb used to express obligation, recommendation, or necessity. In persuasive writing or speech, it adds a sense of strong conviction and implies that the action being advocated for is the morally right thing to do.
Related terms
Modality: Modality refers to how certain or probable something is expressed in language. Modal verbs like "should," "must," and "could" are examples of modality.
Ethos is one of Aristotle's rhetorical appeals and refers to the ethical or moral character established by an author or speaker in order to gain credibility with their audience.
Moral imperative: A moral imperative is a principle or belief that one must follow because it is morally obligatory or necessary. It often involves using words like "ought," "must," or "should."