Hmmmm, I wonder if we aren't putting the cannibalism before the mythology here? Did ogres become (chaotic) because they practised cannibalism, or did they practise cannibalism in order to become ogres?
To me, the latter seems more likely. It was the great darkness, all was loss, starvation, despair, and no doubt people sought out anything that would let them survive, and since chaos seemed to be 'winning' no doubt some sought to join it. Cacodaemon seems like one of the more comprehensible of the chaos gods. He'll grant you great powers, turning you into a sort of super-man....all he asks is that you show your devotion to him with sacrifice--on the surface not so different from many gods.
It is just that the sacrifice he asks for breaks a powerful taboo. Which really raises the question, is it that Cacodaemon really enjoys cannibalism, or is that, being a chaos god and all, he sought to break down the remnants of society by asking his followers to break one of the fundamental taboos of their societies, a taboo whose violation was bound to erode trust and sense of community? (well, it could be both I suppose).
I'd view Cacodaemon as a sort of advance column of the chaos gods. Societies that were strong enough to resist the more blatant assaults of chaos could perhaps be weakened and even fractured if he could tempt some into worshipping him. The shambles that would eventually remain would be easy prey for all sorts of chaos.
Part of this could be that ogres know they are doing 'wrong,' but they choose to do so for their personal gain.
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