That the teacher was unaware of the content of the film is the real problem in my eyes.
Mind you, I've made no secret of being a practitioner of BDSM in here, so clear my views on this are a little skewed (mainly insofar as I find the book to be poorly written and a HORRIBLE illustration of the BDSM lifestyle)
But, were the class to be assigned, say, to read Justine I would have no problem with it, assuming, of course, the students were say 17 or older.
Many of you may disagree with me on this, however, in addition to being one of the seminal works of the Marquis de Sade, it is also regarded by many to be historically significant literature. Banning it, to me, is as foolish as banning Tom Sawyer for N---er Jim.
Mind you, this is a complete tangent to the discussion, which should begin and end with the following statement:
"50 Shade of Gray is terrible, knows nothing of the lifestyle it talks about, and isn't even fit as bog-roll replacement."