One of the themes of Animal Farm is the misuse of language to create propaganda—and the need for ordinary people (or animals) to be alert to how they are being manipulated so that it cannot happen.
From the start, the pigs take advantage of the fact that they are more intelligent than the other animals to commandeer the milk and the windfall apples for themselves rather than dividing them equally among all the animals. As they always will, they have an excuse: they need the food for all the brainwork they are engaged it—work they claim they do for the benefit of the other animals. And they also use fear, an important component of propaganda, to get their way. As Squealer explains,
Day and night we are watching over your welfare. It is for YOUR sake that we drink that milk and eat those apples. Do you know what would happen if we pigs failed in our duty? Jones would come back!
The other animals are too quick to accept that explanation and not push back with their own need for food based on the physical labor they do.
After Napoleon seizes power, the propaganda escalates. Squealer, who can always spin things in favor of the pigs, becomes even more important in his role as the chief propagandist. As the animals say, "he could turn black into white."
When Napoleon, for example, ends the debates at the weekly farm meetings in favor of simply handing out orders, Squealer puts a propaganda spin on this loss of rights, saying,
I trust that every animal here appreciates the sacrifice that Comrade Napoleon has made in taking this extra labour upon himself. Do not imagine, comrades, that leadership is a pleasure! On the contrary, it is a deep and heavy responsibility. No one believes more firmly than Comrade Napoleon that all animals are equal. He would be only too happy to let you make your decisions for yourselves. But sometimes you might make the wrong decisions, comrades, and then where should we be?
This kind of twisting of the truth and fear-mongering to serve the interests of the pigs goes on until finally the Seven Commandments are reduced to one, and that one is a logical contradiction:
ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS
The book warns against allowing the slippery slope of propaganda to lead to tyranny and oppression.