Take law and order. The Upper and Lower Classes both desire to avoid paying the consequences of breaking the law. The Uppers believe in "special rules for special people." The law exists to protect them from those who would prey upon them; it has no business questioning how they run their own lives. Meanwhile, the Lowers live in fear of the police and what those in authority will make of their doings. Even if not guilty of anything, the Lowers will tend to avoid dealing with the police, will be reluctant to snitch on others, and will tend to argue that they're not doing any real harm and so the police should have better things to do than to hassle them. The Middlers advanced the concept of the rule of law -- that we have a government of laws and not of men, that everyone is equal (and equally responsible) before the law -- and they are the ones who insist upon it, because the law was their great bulwark against the Uppers who would have lumped them in with the Lowers and run roughshod over them.
Or take sexual behavior and marriage customs. For the Uppers, marriage was always more about property and succession than about love. In England, the gentry talked openly of "the marriage market." This led to the practice of condoning all kinds of on-the-side relationships, so long as they didn't endanger the property or the succession. Meanwhile, among the Lowers, relationships tended to be bound only by the interest of the parties. Many Lower Class folk never got formally married, so it wasn't hard to break up a household and establish a new one. Even among those formally married, easy divorce was desirable, since the only thing holding the relationship together was the desire of both parties. The Middlers were different. They wanted both order and love; or, at least, they wanted respectability. How one ordered one's life reflected upon one's reliability and status in a society where those mattered most, so the Middle Class were all about the stability of marriage and the importance of family. Which is not to say that Middle Class folk are less likely to commit fornication or adultery; just that they are more likely to worry about what others will think of them.
Or take the regulation of business and fair trade practices. Poor folk expect to be cheated. Rich folk expect to do what they like and hire lawyers to keep them on the right side of the law. The rich also do not scruple to run others out of business, if they are in their way. It is the Middle Class who insisted on fair trade rules and equal access to the courts and reliable weights and measures and all the rest of it. The Middle Class run Small Business, which can only compete with Big Business if all dealings are open and fair. Small Business needs government to play fair, too. Neither the rich nor the poor expect or want the government to play fair. They're looking for some kind of loophole.
One could multiply examples. The intent of these is not to paint the Middle Class as more virtuous than the other classes, just to point out that they are very different in their values from the other classes. The other two classes see the Middle Class as hypocritical or self-righteous. This is a constant theme of "hip" comedians and liberal talk show hosts (e.g., Bill Maher, Whoopi Goldberg, inter alii). But at bottom, all three classes agree that the Middle Class is different. This also explains why rich politicians and fabulously wealthy celebrities can get away with acting as Tribunes of the poor by calling out those they see as the stuffy, oppressive, bigoted, plain white bread types that they think keep minorities, women, and the sexually adventurous in bondage. Both ends unite against the middle.