No, I don't think Jimbo is dangerous.
Sometimes I even wonder if Jack was right about Jimbo. Jack very well may have known more about Jimbo to encourage him to approach him at the bar. And, there's a moment when Jack and Jimbo lock eyes for a second where there's something interesting in Jimbo's eyes. It seems possible that Jimbo rejects Jack because the bartender is hovering so close and watching so close. And, he may have also been nervous because there were so many other people around (again my point about how hard it can be to find and connect with a partner as a single gay person).
Jimbo may genuinely have been rejecting Jack because he was straight... but he may also have just been another scared gay man.
That is exactly what I have always thought.Jack picked the right man, but in completely the wrong circumstances.To try and pick up a man in a bar full of macho type men
right under the eye of a very suspicious barman, was reckless.But then Jack's character is reckless.
I suspect to cover his own tracks/sexuality, Jimbo goes back to the men and is undoubtedly less than pleasant about Jack, to allay any suspicion, we already know it was a very hard time and place to be gay.
I assume that a lot of men were like Ennis terrified of the consequences, Proulx herself said that the idea 1st came to her by seeing a man in a bar, totally on his own.
I sense no danger, just the humiliation of Jack, by Jimbo to cover himself. Jack subjects himself to humiliation on many an occassion by going to Mexico and paying for sex.
That too is a big difference between him and Ennis, Jack seems to have a much higher libido, but after the reunion scene, I think for Jack the sex with other men is just that.He can separate sex from love, in the way a lot of men, gay or straight can.
I often find myself wondering, had they got together permanantly, would Jack have remained sexually faithful. He seems character wise, to need the extra edge.
Jack's gaydar for want of a better word seems prety accurate, he sees what lies beneath with Ennis and even with Randal. I see no reason why a gay man should be any less astute than a straight man or woman. Most people know from subtle gestures etc, when soemone is interested in them.
So probably right call, but foolhardy place to attempt it.
If Jack can spot the sexuality, in someone as closed as Ennis, I suspect he can spot a less closed gay man at 50 paces.But as always with Jack, there is that need to be reckless.