Proulx was right when she said that young people who are still a bit insecure/uncomfortable about sexuality will probably not see this film. Just like the young Ennis and Jack...
According to the article, some of the young men interviewed will have no problem seeing the film with their girlfriends, but will have a problem seeing it with a good male friend because people would think that they were gay lovers.
This only shows that they are not yet mature enough to be sure or comfortable with their own sexuality without reference to what other people (like their peers) may think of them.
In other words: if you are straight, you are straight. Will the opinion of other people affect or change this? It is indeed a question of insecurity.