i never saw oni as evil. paranoid and prone to "the ends justified the means" line of thinking but to think back pre-war and the growth of humanity after the jungle wars when we had centuries of united rule and these entitled colonist who think that they are too far from the homeland for them to be from the homeland. begin create organizations the range of protest movement to arm rebellions, terrorist and piracy. many of these organizations are competing. which to the unified government at the time was the greatest threat in the galaxy to human progress. then the covenant was a thing. some innes returned to fold but most were just left to die. and now the covenant are gone and this new and rather far more vicious N.C.A has become the greatest threat to human progress and now humans have access to galaxy cleaning super weapons in the halo rings. so knock the unsc/ oni as much as you want but i fear this new threat and the chief would see them as a threat also. but that's just my interpretation