I think anyone who can be comfortable with their sexuality and have a sense of compassion will feel deeply for Jack and Ennis. It's a time-tested love story, just told with a different twist. For people who have been in love and remember those first encounters together, BBM reminds them of that energy and the passion. What is interesting about this story, apart from the conventional Hollywood romance method, is that there is no support network for either Jack or Ennis. No catty "best friend" role to serve as comic relief and the eye rolling encourager. In fact, they have NO ONE at all but each other. In fact, it almost seems they have no friends either, excepting perhaps Jack's new found Texas friend that we see very little of in the film. It adds to the isolation which seems to be a theme of this film anyway.
Whoa, I never thought about that. I mean, I realized how lonely the two were but I completely forgot how (thankfully) void this film was of the standard best friend role. Another thing I really like about this movie!
And I always saw Jack and Ennis as best friends. It's just obvious they were. They were soul mates, lovers, and best friends. As for whether or not they're gay, that's not exactly easy for me to answer. I think they were both gay myself (although I do believe Kinsey's theories on sexuality have a lot of credibility). I mean, they certainly didn't mind having sex with women but I don't think they got any substantial thrill out of it.
And as for their first sexual encounter (you mention it as though they only have sex once, OP), I think -- if this makes
any sense -- that there was definitely emotion behind it, and they both were very (maybe subconsciously) attracted to each other but their lust for each other drove their actions. Essentially, I think they yearned for each other both physically and emotionally.