Using ethos: The animals must rely on the pigs to run the farm; no other animals have the leadership skill necessary. They are the most intelligent, the most cunning, the most ambitious, and the most persuasive. The pigs are the ones who have the mettle to defend the farm if Jones or anyone else tries to attack it. The animals feel a sense of security under the rule of the pigs because they know the pigs are the saavy ones who can keep the farm under animal rule. The pigs always make it their number one priority to keep the farm safe from outside intruders; therefore, sometimes they must go to great measures, even bending the commandments at times, to make sure this happens.
Using logos: The pigs comfort must come first because they are brain animals. They need to have more apples to be able to utilize their great brainpower to the highest extent. They also have the most important and difficult job to lead the farm. In order for them to lead effectively and maintain the long hours it takes, the pigs must be the most comfortable, hence the need to sleep in the farmhouse. Finally, the rule against making deals with humans was meant to protect the lower level animals from being taken advantage of. The pigs, being so intelligent, are therefore exempt from this rule, because the have the mental means necessary to hold their own against the animals.
Using pathos: The animals only have to look at the hard lives they live, all the loved ones they lost, and all the valuables they sacrificed to Jones. Without Jones, those hardships won't exist. You may still feel now, after the revolution, that these things are still occuring, but they are all for the good of tomorrow. What we sacrifice now will be our joys and successes tenfold down the road. While we gave and gave and never received in the day of Jones' rule, the animals will undoubtedly profit down the road from the labors they put forth now.