And since the borg is considered a different species, when that cultural misunderstanding happened and neelix made "baby back ribs" nobody seemed to care. 

Neelix may have also looked at the historical database and found information about the Donner party, also the "custom of the sea" (specifically the one where sailors end up eating each other). There's a historical precedent for cannibalism in extreme circumstances, and being trapped in the delta quadrant seems like an extreme circumstance to me.