Actually, this is feel-good nonsense.

Pretty much every society has treated at least some of those over whom it has power over very, very poorly:

Assyria,

Persia,

Greece,

Rome,

Han China,

Franks,

Arab Empire,

Mongols,

Ottomans,

Spanish,

French,

British,

Belgians,

Germans,

Swedes,

Norwegians,

Soviets,

Americans,