The first conversation about marriage takes place in chapter 1. Daisy playfully suggests that she will "arrange a marriage" between Jordan and Nick. Daisy says that Nick should visit her and Jordan often so that she can "fling [them] together." After Tom then says that Jordan's family shouldn't "let her run around the country this way," Daisy says that Nick will "look after" Jordan, and that "the home influence will be very good" for Jordan. Marriage in this conversation is presented as a means by which to anchor and tame Jordan. Jordan is a very willful character who seems to enjoy her freedom and independence. However, in the 1920s, despite women having recently gained the vote, the prevailing opinion was that women should exist in the domestic sphere, as wives and mothers. Jordan exists outside of this sphere and is thus regarded as more masculine than feminine and as more abnormal than normal. Marriage here is seen as way to restrain and normalize Jordan and thus as a way to make her into a more socially acceptable woman.
Later in the novel, in chapter 7, Tom launches into a tirade against people like Gatsby, whom he sees as "sneering at family life and family institutions." Tom, rather hypocritically, given his affair with Myrtle, imagines that society is on a slippery slope to some kind of amoral dystopian future, the culmination of which is "intermarriage between black and white." Tom's attitude here towards interracial marriage is indicative of a rise in racist attitudes in the 1920s. Indeed, in 1915, The Birth of a Nation became the highest grossing movie in America, and it was only overtaken twenty-four years later, in 1939, by Gone With The Wind. The Birth of a Nation presented black people as animalistic, violent rapists and presented the KKK as brave and noble heroes. Tom Buchanan, judging by his attitude towards interracial marriage, would likely have been among those who counted themselves fans of The Birth of a Nation.