Their only outlet is to fight to retain what little they have. Most families will not complain to the government about their landlords for fear of losing their homes, as Orwell points out in chapter 4. This mentality has seeped into the middle class without their noticing. Increasingly, Orwell claims, the middle class value their possessions and hold them as badges, certifying their status. They fight violently to ensure their class is established.
Fear motivates the middle class to stay above the lower class.
Orwell demonstrates this in chapter 10. They pass this fear off as disgust or disdain for the dirty, smelly workers, but in truth, it is ignorance and fear. Ironically, the middle class usually defends those who exploit them rather than side with the working class. Of course, many of the habits of the middle class seem sickly and wasteful to the working class, so the intolerance can go both ways. Instead of joining with the other oppressed people of the working class, they pass the oppression down onto them.