Let me have my say.
"Brokeback" advances cowboy culture and American civilization unlike any other movie I have ever seen.
"Brokeback" is not about "gay cowboys". It is about human love in all its forms, male and female, parent and child.
"Brokeback" has a heroic, Homeric quality, in which the full range of the characters' humanity is allowed to be expressed (that's why the initial lovemaking scene is so important).
Whether someone assumes the passive position with another man or whether someone lives in a broken down trailer is seen as irrelevant. What matters is the depth of feeling one human being has for another.