These are all propaganda techniques, or logical fallacies. Ad populum means that everyone believes it’s true, so it must be true. An example of this is the exploitation of Snowball. Everyone believes that Snowball was a traitor, so therefore he must be a traitor!
Two wrongs make a right means if one wrong is committed, it can be corrected with another wrong. It basically means that you are making an excuse for the fact that one person did something wrong, but another person did something wrong so it must be all right. For example, when the animals run out of food so the pigs respond but cutting rations.
Guilt by association is common in totalitarian regimes. It basically means that people who are part of a group are all guilty, or people associated with the “guilty” are all guilty. For example, those who were supporters of Snowball were executed. Another example is when several geese were executed.
Ad hominem is the idea of attacking a person’s character instead of his ideas. It can often result in slinging insults instead of actually debating facts. For example, criticisms of Snowball were ad hominem because Napoleon could not attack his ideas.