In Chapter 1, Tom directly says, "Civilization's going to pieces ... I've gotten to be a terrible pessimist about things." Tom then goes on to explain the findings of a terribly racist book, The Rise of the Colored Empires, which argued, incorrectly that the "Nordics," or white people, "are the dominant race" and that they have "produced all the things that go to make civilization—oh, science and art, and all that."
This racist, ignorant rant shows several things about Tom, most evident are his dual feelings of superiority and entitlement, which are on display throughout The Great Gatsby.
While the book Tom cites is not about social class, it is still applicable in that people like Gatsby, Myrtle and George are not like him and Daisy in that they have to work to make their money. They are part of the reason society is "going to pieces."
In the novel, Tom looks down on everyone who is not from his social class. He looks down on Gatsby as one of the "newly rich" and accuses him (accurately) of being "some big bootlegger."
Another major example of Tom expressing his superiority is when he feels free to strike Myrtle breaking her nose because he did not like what she was saying.
In addition, Daisy shares the same traits of superiority and entitlement as Tom. When she attends one of Gatsby's parties, she does not have a good time because she was "appalled by West Egg," the new moneyed place across the bay that represents those who earned their wealth instead of inheriting their money.