Yes. Propaganda is effective to pursuade the animals or maybe the animals just lose control or confidence in the fact that they are able to stand together for what they want or believe in.
Napolean and Snowball use propaganda to further their own agendas. They do not care that the other animals will be suffering. The propaganda is effective because it serves to deceive most of the animals and to convince them to tolerate horrid living conditions, to even turn on the humans and to trust the very leaders that are starving them to death.