In the first chapter, what does Tom's behavior reveal about his character?

Nick Carraway, the narrator of "The Great Gatsby" by F. Scott Fitzgerald, describes Tom Buchanan as a powerful man who reached a

limited excellence at twenty-one that [makes] everything afterwards savours of anti-climax....he'd brought down a string of polo ponies from Lake Forest [wealthy suburb of Chicago].  It was hard to realize that a manin my own generation was wealthy enough to do that.

Now, Nick narrates, Tom has changed.  He is a

straw haired man of thirty with a hard mouth and a supercilious manner [and] enourmous power of body.  It was a body capable of enormous leverage--a cruel body. His speaking voice, a gruff husky tenor, added to the impression of fractiousness he conveyed.  There was a touch of paternal contempt in it...

Later, Tom, clearly a brute of a man, proudly displays his property to Nick:  land, stables, etc., and then initiates a discussion about the book he is reading.  This book is entitled "The Rise of the Colored Empires," and Tom is in accord with the author's contention that the white race is going to be overtaken by the black race, arguing that the idea is scientific. 

Shortly after this, the phone rings and the butler calls Tom. As Daisy rushes from the room, too, Jordan Baker, an athletic friend of Daisy Buchanan, offhandedly gives Nick the news that Tom is conducting an affair with Myrtle Wilson.  Appalled, Tom feels that he should tell Daisy to "rush out of the house," avoiding this immoral situation. But, he remains and talks with Daisy, learning that Tom was not even around when she gave birth to their daughter. As Daisy talks with him, Tom feels "the basic insincerity of what she said."  When he leaves, Nick is cautioned by Tom, "Don't believe everything you hear."

As Nick returns home, he reflects on his father's words,

Whenever you feel like criticizing anyone, just remember that all the people in the world haven't had the advantages that you have had.

Nick realizes that money is not what gives people value.  Rather, it is their inherent decency and integrity. Already Tom Buchanan is working on establishing himself as the villain of this novel.