I'd assume that it stems from a few places. One of them would probably be the "White Mans Burden", but another would probably be that uncivilized tribes don't h

I'd assume that it stems from a few places. One of them would probably be the "White Mans Burden", but another would probably be that uncivilized tribes don't have guns to shoot back with and so using modern weaponry against them will end in a lot of deaths.