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,

You think present day America should be judged by the same standards as Genghis Khan‘s Mongol Empire?

Yeah, we're worse. They raised hell for sure but so far as civilization building goes they have most of us anglos beat.

How is this feel good nonsense? There's no feelz involved, other than your response.

You think it is justified behavior because 'others do it'. Not sure that's how morality or judgement of societies works. The fact that your immediate response is to defend the behavior based on appeals to 'but others do it' not on the basis of actual morality just re-enforces my point.