When Byron's trying to free Greece (and he died trying, in 1823, which left the British with a real legendary status in Greece, up until WWII when Churchill diverted resources elsewhere rather than lending them to the Greek struggle against the Nazis) what he actually says quite clearly is that the unheroic stuff is a consequence of the oppression they've suffered; that is, he's looking at the effects of post-colonialism and being very clear-eyed and realistic about them, and not blaming people for it.