The Great Gatsby is, in part, Fitzgerald's commentary on the morality of the rich. The afternoon in New York, at the party held by Myrtle and Tom in their illicit "love nest," is a picture of the immorality of both the rich and the poor. I think it's safe to say Nick did not enjoy his time at the party, and we have several clues that this is true. First, it confirms in a very real and tangible way the fact that his cousin's husband is cheating on her. Second, the apartment and Myrtle are both just not quite right, making it uncomfortable for Nick who knows it. The furniture is classy but it's way too large for the small apartment; Myrtle has money to spend (because of Tom) and buys cheap perfume, a mutt, and gossip magazines--and wants to ride in the lavender taxi. It's all just off, and Nick is unsettled by it--as he is by being a third wheel at the beginning of this event. Third, Nick does have a conscience and sees, when they are at Wilson's Garage, that this is a cruel action on a rather helpless man. Fourth, he is appalled by Tom's behavior toward Myrtle. Tom punches Myrtle in the nose, something no man should be any more comfortable watching than doing. He learns that Tom has not only lied to Daisy, he has also lied to Myrtle, telling her he can't divorce Daisy because they're Catholic. Finally, though he is not accustomed to drinking, he gets drunk at this event. The guests are strange, the environment is strange, the behaviors are worse than strange, and there is no doubt Tom finds the entire episode uncomfortable. It's worth noting that he doesn't make much of an effort to leave; however, it's not anything he'd like to repeat, I'm certain.