What does Tom condemn?

Tom is an arrogant, intolerant man. His comments in the book frequently demonstrate his thorough contempt for African Americans and other minorities, as well as other people he deems inferior because of their social class (Myrtle's Wilson's husband, for example). These prejudices color his most thorough condemnation: the affair between Gatsby and Daisy. He describes their affair as an instance of what he perceives as society's decline:

I suppose the latest thing is to sit back and let Mr. Nobody from Nowhere make love to your wife. Well, if that's the idea, you can count me out. . . . Nowadays people begin by sneering at family life and family institutions, and next they'll throw everything overboard and have intermarriage between black and white.

Note that his condemnation is not simply an accusation of infidelity. Tom himself has been carrying on an affair with Myrtle Wilson. Rather it is that Gatsby is a "Nobody" from "Nowhere" who is clearly inferior in Tom's mind. The affair is evidence, in a way that Tom's own dalliance is not, of the decline of society. The conversation that led to this condemnation began by Tom questioning Gatsby's time at Oxford and culminates with Gatsby telling Tom that Daisy never loved him. Tom has already condemned Gatsby's alleged associations with the gangster Meyer Wolfsheim. So his hatred for Gatsby goes beyond his anger that the man has had an affair with his wife. Gatsby represents much of what Tom hates in the world and is, in Tom's eyes, beneath him.

Tom Buchanan condemns several things and people throughout the novel The Great Gatsby. In chapter 1, Tom goes on a rant condemning civilization and the influence of other races. Tom's racist personality is revealed as he tells Nick, Daisy, and Jordan that colored people are ruining civilization. Tom urges his guests to read "The Rise of the Colored Empires," which explores how other races are attempting to suppress the "white race."
In chapter 7, Tom Buchanan also condemns Jay Gatsby's illegal business ventures. Tom exposes Jay Gatsby as a bootlegger in front of Daisy, Jordan, and Nick during their visit to New York City. Tom condemns Gatsby for being in business with Meyer Wolfsheim and selling grain alcohol over the counter at drug stores. Tom also condemns the fact that Gatsby allowed his friend, Walter Chase, to go to jail for a month. Tom then proceeds to criticize Gatsby for his false identity and manufactured personality before everyone leaves the city.