Talk about blaming the victim: it sounds a lot like Orwell is faulting the lower-class animals for not being smart enough to realize what's going on. Either they fail to recognize their oppression, or they ignore it because they want to wear ribbons in their hair (ahem, Molly). But you could also see the pigs as having follies of their own. A drunk pig stumbling around on two legs? Sounds pretty foolish to us.
The lower-class animals end up oppressed not just because the pigs are mean to them (although they are) but because they're inherently idiots.
The pigs may be more intelligent than the rest of the animals, but the humans ultimately make them into fools.