I find it interesting to read everyone's opinion about this subject. You can look at this story from so many perspectives!
So if bull riders and rodeo clowns didn't like eachother so much, than its not an akward thing what happened to Jack in the bar with the clown. But this scene comes to me like if Jimbo the clown already had his doubts about Jack, before he offered him a drink. It seemed he wanted to keep him on a distance, maybe he heard things about him. Also, mr. Newsome didn't like him: he reffered to his rodeo past, like if rodeo is something for softies, and off course the dinner/tv scene, where he also implicates that Jack isn't a real man or something. To me , rodeo seems something for tough guys, its dangerous, and you have to be strong.
But maybe people in that time looked down on the bull riders in an way of: they are only after the money and they don't like to work for it.
Maybe that was also mr. Newsome's way of looking at Jack.
In the movie/story, there are various scenes where other people seem to disregard Jack, so its an effect that he has on certain people. But, on the other hand, Jack also has an attraction on people like Ennis, Randall and Lureen. So what's the diffrence between those people?
I think it has to do with status and setted ways of interaction between groups ( bad understanding: clowns/bull riders and rich/poor) and the people who loved Jack had other motives: with Ennis it was love, wich wasn't a motive but a force of nature, i think in the beginning with Lureen also love, and with Randall it was an adventure, but not a love relation.
The movie/story only shows particular parts of the story, but off course, there happened a lot more things.
And that's good that we don't know them, because in a story written like Lord of the Rings, nothing is left to your fantasie and everything is fixed. Not that lotr is bad, actually i have seen it and read it over and over again, but it has not such an impact on me as BBM.
But my point is in this topic: the Jimbo scene tells me that in that particular rodeo camp ( or how you want to call it) there where rumours about Jack wich Jimbo had heard. It was not only the the (unwritten) rule that clowns and bull riders don't have a beer together. I can't imagine that only buying a beer for someone of the same sex implicates that he wants something from you, even not in that time. Maybe someone who was young in these days can tell something about this.
To me, and for everyone on this forum i guess, the whole movie is also interesting because of the numerous questions you can ask yourself about it.