Well, this is either the exact thing or pretty close to the thing that you and I have argued about before, Jeff. And as I recall, I lost the last time. But what the hell, I'm always up for an argument.
I do agree with this:
And calling Jack a "boy" is a definite disparagement in this context, coming out of Ennis's anger.
Ennis is angry, and "boy" is disparaging, and "boys like you" (as opposed to "us") can be read as distinguishing Jack from Ennis in some way.
But I am still reluctant to go along with the idea that Ennis is consciously speaking in code, that boy and man refer to sexual positions, that Ennis equates receiving with queerness but does not attach a stigma to delivering. Of course you know much more about gay culture than I do, and if someone you know in real life said something like that perhaps the meaning would be clear to everybody. But you also know much more about it than Ennis does. He knows basically nothing outside of his private experiences with Jack (that he even has heard what they have in Mexico stretches credulity a bit).
Jeff, I remember your pointing out the larger, male-culture stigma about "receiving," and I get that. But if you ask me, Ennis considers himself to have crossed a pretty big line from the get-go. If he's willing to go there, who knows what else he might do. Or at least think. So what Ennis thinks about their relationship, to what extent he considers his and Jack's sexuality different -- all those issues are hazier to me than they are to you guys. Partly for the obvious reasons, I guess, but also partly because you're making what I consider an interpretive leap. In my mind, Ennis is sort of feeling his way along in the relationship, not being guided by any external norms but just by whatever unfolds between them, trying not to think too much about what it all implies.
Also, if I understand correctly, your interpretation suggests that Ennis feels a certain amount of contempt for Jack (Jack is a "boy," Ennis is a "man," Jack is "queer," Ennis prides himself on not being), and aside from this one remark I see no other sign anywhere in the movie that he does.
Now I steel myself for the reply that I couldn't possibly know anything about this. And it's true that my knowledge is inevitably limited. But Jeff, I also think your interpretation is colored by the way you see the whole scene (Mark, I don't know how you feel about this): that Ennis' breakdown is triggered by having to confront the truth about his sexuality. In that context, your reading of that line makes sense; Ennis' threat is a desperate attempt to separate himself from Jack in that respect. And I'm not saying that interpretation is "wrong" -- obviously it works for you.
But if you see the scene the way I do, which is that Ennis breaks down because he's afraid of losing Jack and can no longer stand the strain their relationship puts on him, then the Mexico remark becomes less significant. It's Ennis lashing angrily out at Jack because that's what Ennis does when he gets upset. And also to deflect the blame for canceling the August trip.
Sorry to yammer on. I told myself a few days ago I was going to start keeping my posts more brief, and until now I was doing pretty well with it.