A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.

Heinlein links everyday civility to cultural health, arguing that the small, habitual courtesies that make social life workable—politeness, consideration, restraint—are not superficial “manners” but a kind of social infrastructure. When those micro-obligations collapse, it signals a deeper erosion of shared norms and mutual recognition. The comparison to a riot is deliberate: riots are visible, episodic crises, but widespread rudeness is diffuse and continuous, indicating that the ordinary bonds of trust and respect have frayed. The quote thus treats manners as an early-warning system for social decay, suggesting that cultural decline is first felt in daily interactions before it becomes dramatic political disorder.