I skimmed the previous posts and I don't think that anyone has mentioned this, and before I do I want to go on record as saying that I believe that both the teacher and the parents are wrong, and yes, I think her parents are milking it, but I'm just offering another opinion.
Does it state anywhere that the gay angle is what "traumatized" this child or is that just what is being assumed? Is that what we are supposed to assume?
Re-playing the movie in my mind to try to figure out what would be so "traumatic" I think that, given the right circumstances, Ennis and Alma in the kitchen after Thanksgiving dinner would be right up there. I've been in a relationship in which I was hit, but, being a tall person I had never seen a man's fist from the low angle that I saw Ennis' fist in the movie, and the first time I saw it, it looked huge to me and it really was something that I did a lot of thinking about. After seeing the movie over and over I realized that the angle wasn't even the way I had experienced it in the beginning, but because I had experienced that in real life it made a big impression on me. I think that there's as much, if not more, likelihood that that scene could have bothered this girl, especially if she had experienced something similar in her own home.