People
It is a folly to expect men to do all that they may reasonably be expected to do.
— Richard Whately
Behind the line May contain spoilers.
Our reading
An editorial interpretation.
A dry observation that people rarely do everything they could sensibly be expected to do, so expecting perfection from them is itself unrealistic. The joke turns on the loop: a reasonable expectation becomes foolish precisely because it is reasonable and still unmet.
Context reviewed