Another thing that bothered me was that in some pieces I sensed a bit of an us vs. them -- i.e., gay vs. straight -- tone. For example, and I wish I had the magazine in front of me but I'm going from month-old memory, there was a mention of the Variety ad and the members of the DCF raising money for it that implied it was an action taken entirely by gay people. Excuse me, but I contributed to that ad, and I know I'm not the only straight person who did.

That approach seems unnecessarily divisive and suggests the writer didn't fully understand how and why viewers were affected by the movie.
I have often puzzled over the appeal of this film and this story to straight women, regardless of age (beyond the obvious points that Brokeback Mountain is an astonishing feat of cinematic art and of short-story writing). 
If you're talking about the erotic aspects as apart from all the other great qualities, I think you can chalk that up as one of the many mysteries of human sexuality. One look at the fanfic forum tells you there are a lot of straight women who find the situation appealing.
I myself am not a big frequenter of the fanfic forum, but I can tell you that it's very compelling to see people of any gender combination expressing love and passion as authentically and movingly as Jack and Ennis do. That in this case they happen to be played by two hot actors doesn't hurt, either.
