So. The Covenant used to believe that the Forerunners believed Humanity to be heretical, and thus launched a 27-year war of genocide.
BUT in Contact Harvest, it is revealed that this is a pretense to prevent knowledge of Humanity's being reclaimers escaping, so apparently the whole thing was a sham.
EXCEPT on Requiem, we learn that the sole surviving Forerunner really does want Humanity destroyed, and the Storm gleefully follows him. So they were right all along, in a roundabout manner. Funny.
[Edited on 11.17.2012 4:59 AM PST]
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Lack of contradicting proof in no way implies validity.