Tastes can change. Ennis goes into camp with Jack Twist thinking he doesn't like soup. But he tries it and likes it. He also enters camp without even considering that he might be homosexual, then he tries Jack and likes that, too.
JACK: It's nobody's business but ours.
Unfortunately, when it comes to homosexuality in this movie, no one minds their own business. But Jack's an idealist, and would love to live in a world where he and Ennis can lead their own private lives.
ENNIS: You know I ain't queer.
JACK: Me neither.
After this exchange, the men immediately start making out in the tent. Actions speak louder than words, guys. But they shun the label "queer" because of its emasculating connotations.
AGUIRRE: You boys sure found a way to make the time pass up there. Twist, you guys wasn't gettin' paid to leave the dogs baby-sit the sheep while you stemmed the rose. Now get the hell out of my trailer.
This is Jack's first encounter with homophobia on-screen. He realizes that Ennis's fear isn't entirely paranoia. People can find out about their love, and harm can come to them because of it.
JIMBO: No thanks, cowboy. If I was to let every rodeo hand I pulled a bull off of buy me liquor, I'd have been an alcoholic long ago. Pulling bulls off you buckaroos is just my job. So save your money for your next entry fee, cowboy.
This encounter with Jimbo the Rodeo Clown foreshadows Jack's death. It could easily go wrong for Jack when Jimbo goes to talk to other men in the corner, men who could turn violent on Jack. Jack isn't stupid, though, and he quickly leaves the bar, preserving his safety.
SINGER: "No one's gonna love you like me."
When Jack and Lureen dance, this is the song they listen to. It should be romantic, but the song would be more appropriate for Jack and Ennis. And if we could peek into Jack's head at this time, it's probably Ennis he is actually thinking about.
ENNIS: I tell ya, there were these two old guys ranched up together down home, Earl and Rich. And they was the joke of town, even though they were pretty tough old birds. Anyway, they…they found Earl dead in an irrigation ditch. Took a tire iron to him, spurred him up and drug him around by his dick till it pulled off. […] Yeah, I was, what, nine years old? My daddy, he made sure me and my brother seen it. Hell, for all I know, he done the job. Two guys livin' together? No way.
This violent flashback explains Ennis's fear of being outed. He's afraid of the same awful violence being perpetrated against himself or against Jack.