IWhoever said that this movie would've received an NC-17 rating if it were about heterosexuals is absolutely right.
I did. I think maybe its just the shock of a male sex scene in a hollywood film that is making people think it was more explicit that it really was. There wasnt really much one could call gratuitous. Most of it was just making out. It was tame... hell, look at the Sharon Stone sex thrillers from the 90's, like Basic Instinct, or Sliver. Those managed to get R ratings (after cutting some footage), yet they were miles beyond anything in Brokeback.
NC-17 is a movie like Showgirls - graphic gratuitous sex, rape scenes, etc.
Now, had this been a child who had been exposed to "the Passion of the Christ" without her parents' permission, the press, liberals, the school and atheists would have been all over it in a heartbeat.
Probably, they would. But of course, many Christians probably would be silent or supportive. Personally, I don't think any school has any business showing either movie (until college level).