Squealer represents the propaganda arm of the controlling class, the pigs. His usual operation is to take whatever the truth is and spin it to show some false evil on the part of Snowball or others, and to show Napoleon as having no flaws at all. He also serves to justify the times when the pigs take more food for themselves, such as the apples and milk, and the times when control of the farm causes the pigs to take more luxuries while denying them to others. One good example of this comes when the pigs move into the farmhouse, an action that had been said to be immoral based on the original tenants of Animalism:
"You have heard then, comrades," he said, "that we pigs now sleep in the beds of the farmhouse? And why not? You did not suppose, surely, that there was ever a ruling against beds? A bed merely means a place to sleep in. A pile of straw in a stall is a bed, properly regarded. The rule was against sheets, which are a human invention."
(Orwell, Animal Farm, msxnet.org)
This sort of moral relativism is seen later as the pigs take more and more of the farm's production for themselves while cutting rations and increasing labor for the other animals. This is a classic failure of the socialist philosophy, since the people organizing and leading will always begin to think of themselves as entitled. Since the workers will need to keep working for their own needs as well as those of the ruling class, more and more burdens will be placed on the workers while the rulers take more and perform less. The Utopian concept of Marxist philosophies collapses as the very real greed of real people takes over; the animals discover this as Napoleon and the pigs become surrogate humans, but far more brutal and efficient.