So the fact that Crash beat Brokeback is supposedly indicative of Hollywood's lack of courage or something, but another way to look at it is that Brokeback's legacy is now safe. Practically every movie that wins a Best Picture honor eventually crumbles under the weight. People realize it's maybe good, but not that good. The consensus becomes that it's overrated, backlash kicks in, and a few years later everyone kind of hates it because they feel like they were duped.
See American Beauty or Titanic. Does anyone really even think about Chicago these days? Think about how many people look back on the year Forrest Gump beat Pulp Fiction and say that Pulp Fiction got robbed. Wouldn't you rather be the movie that got robbed that everyone still loves, rather than the movie that makes everybody wonder what they were so excited about?
If Brokeback is actually a good movie, in a few years everyone will still think so, and it will be free of the increased scrutiny that will doom it to severe backlash. In fact, it's likely to be viewed with extra charity since it was an overlooked gem (a massively hyped overlooked gem, perhaps, but overlooked nonetheless). Meanwhile, the Best Picture Oscar virtually guarantees that viewers will eventually realize that Crash is an empty shell that flatters people into believing they've seen something important.