Interesting observation but not born out by the chronology of the involvements in the film. I think the marriages, divorces etc post dated the relationship between the main characters. But it was a while ago I saw it.
That Liberal Arts student needs to get an education about life before analyzing movies. Brokeback Mountain was obviously about the frustrations of expressing love when you do it in a manner that society frowns upon. Sure, it included adultery but that sure was not the focus of the movie. The focus was the destructiveness forced upon two people who were in love but were not able to overcome societal pressures. It was a tragedy for all involved (men and women) who had to live a lie.
Crash was a great movie, too. Yes, it was about racism. But, it was also a great movie in showing the CRACKS in racism where one's humanity rose up and overcame it.