Sedaris writes in an understated but satiric tone while observing the people surrounding him, their conformity to social norms, and their attempts to force those norms upon others.
His purpose, from the opening of Me Talk Pretty One Day, is to show that authority figures have used indirect methods of stigmatizing otherness. Two episodes can be cited to illustrate this dynamic.
In the 1960s, speech class was a kind of mechanism by which children (although Sedaris mentions only boys in this context, girls were subjected to it as well) were singled out as different and, in some sense, deficient because of the way they talked. In Sedaris's school, Miss Samson, the speech teacher, is likened to an FBI agent making an arrest when she comes into the classroom and singles him out. Though his writing is wry and low-key, Sedaris's style uses metaphor and hyperbole to get his point across. The subtext of the episode is that boys who are suspected of being gay (or potentially so) are identified by lisping or some other alleged abnormality of speech.
These attempts to enforce conformity are contextualized in the outwardly benign milieu of a middle-class upbringing, typical of the time and yet alienating to someone such as Sedaris, who feels from an early point that he's different and is being singled out. His descriptions are ironic, since the people tasked with enforcing conformity have some aspect of otherness themselves. Miss Samson feels herself a failure as a speech teacher. The guitar teacher, Mister Mancini, is a little person. Sedaris witnesses a scene at the mall where Mancini is laughed at by some boys, yet when Sedaris behaves in what is considered an "inappropriate" way by singing a jingle from a TV commercial, Mancini himself upbraids Sedaris, telling him, "I'm not into that scene." Again, a behavior is being identified as characteristic of gay people without this being stated openly.
Two themes identifiable here are indirection and deflection. Criticism of boys who don't seem "normal" is done in a way that veils the actual reason for it. At the same time, some people who themselves are "different," such as Mancini, often try to deflect attention from themselves by criticizing others for allegedly non-conformist behavior, as Mancini does to the young Sedaris.
A small stylistic point, but a significant one, is that "Mister" is always written out for Mancini rather than given its usual abbreviated form. The effect is to further satirize an authority figure, a member of the establishment enforcing the conformity that was considered so vital at that time and unfortunately, in many quarters, still is.