There is a lot of stuff here.
Jack was certainly liked by the the ranch foreman. And, of course, he is liked by Ennis. So, the implication is that he is not hated by all other men. He is not liked by other men for different reasons.
For example, he does not get respect from the farmer clients at Lureen's office because they look down on rodeo f*ckups.
He is not liked by the rodeo clown because (presumably) he is straight, and he senses an erotic frisson from Jack that makes him uncomfortable.
He is not liked by Lureen's father because he thinks his daughter deserves better -- as far as social and monetary things go.
His not being liked by his father is a more complicated story. His father seems to have decided for himself that Jack was not good helping out at the ranch. But I am sure the real problem here is not with Jack, but with his father.
To tell his father that he was divorcing his wife and moving back in with a man -- sharing a cabin: I think that in John Twist's world, that is tantamount to admiting queerness. IMO, John Twist knew, as much as his wife knew.
Gyllenhaal's Jack Twist has a lot of heart, sympathy, and angst. This Jack Twist bears the unmistakable stamp of Jake Gyllenhaal's classic roles.
Some would interpret this projected persona as effeminacy ('the doe-eyed indie wimp', as some crass people are wont to call it.) I call it
sensitivity. I call it receptivity. Proulx calls it a 'quicksilver' quality.
Gyllenhaal's Jack Twist wears his heart in his sleeve. He is therefore made vulnerable because of this. Some of the characters naturally looked at this as a weakness. But for Ledger's Ennis, this openness was the very kernel of his heart's desire.
This is why I love Jack.