Great discussion, what might actually have been going on out West as far as "respectability" and who defined it. Of course, it was different in every area, different in every community really, different in everyone's perception; and then we don't know the truth of history anyway, as monicita said. And then factor in all those others: blacks, Asians, Mexicans, others, with their own cultural values -- who knows?? And we really do have to separate different eras, too -- things do change so much so fast.
Then, WW, I'm chuckling at the Englishwoman telling us about American history.

Thank you, righto. And you're so right about women coming out West or being sent over here from elsewhere in order to be the domestics for the men out West. I forgot about that. I forgot that those men did
not do their own cooking and laundry and all that! And that someone to have kids to grow up to be more workers was desireable, too. I still bet there were respectable "straight" bachelors around who wouldn't be persecuted.
(What about in Lake Wobegon? The "Norweigan bachelor farmers" he talks about

They weren't gay, they were just bachelors. Hmmm...Ennis and Jack in Lake Wobegon?)
But back to Ennis, it was an interesting period -- he and Jack were just short of being baby boomers -- pretty funny, that. Though born in 1944, presumably, they were still of the post-war generation like some of us, and things were jumping over here during that time. But things jumped differently out in rural west...and it all comes down to his own perceptions anyway.
It occurs to me that a big thing that was happening during that time, post-war, was that the men came home and pushed the women out of the workforce where they'd had independence, stuck them back in the kitchen and to have babies (us). It's too complex, how that factors into social mores of the times, but certainly the "nuclear family" was supposedly the ideal in Ennis and Jack's parents' time, so any variant wasn't going to fit in.
As to if he was actually homosexually inclined from birth or not, I don't really see strong evidence in the movie or story of him being any more gay than the next boy. I would think most boys messed around with other boys a little (like the girls I knew of, with the girls), and then a bit older, thought about it at the least...and I can't imagine any other young man similar to Ennis being in that situation with Jack and not acting on it. I think the men here might answer this better, could know how it feels to be a young boy, not quickened by adolescence even yet, and starting to feel gay...
But I keep forgetting -- I am really not a good judge of this. I forget that really religious people were different, and sometimes it was so strong that even the rebelliousness of youth couldn't break through the religious conditioning. I grew up in the city, experimented with different religions or none, including Eastern thought and such that my dad had books about, dad the jazz piano player, etc., etc. So I just can't say what life was like for my peers who didn't live in big cities in comfortable enough conditions that allowed for some amount of freedom.
Anyway, I like talking about this subject (teacher don't like me -- I talk too much) but I don't require an answer for myself. I'm just glad Ennis found this kind of love for himself even considering the outcome...
kathy