Oh man, here's the impetus for a new low price air carrier, Squid Games Airlines.

I know perfectly well that legality is different from ethics. But in common sense terms, charging money for what you don't intend to offer is fraud.

They did intend to offer it when it was sold. Even in this scenario it was well understood that the added United employees were last minute. This is even more cut and dry not fraud than regular overbooking that results in a shortage purely from customer sales.

Then that's still United's own fault for not planning their employee shuttling properly.

They're an airline, get another plane, maybe even a charter if their employees' travel is important enough for them to justify brutalizing their paying customers.