In today's New York Times, A.O. Scott has an article, Take the Kids, and Don't Feel Guilty, which you might find interesting.
His central argument is two-fold. Parents should look beyond easy rules of thumb in deciding what is beneficial for their children. Yes, we should seek age appropriate materials (movies in the case of his article and books in the case of TTMD). But we should be simultaneously seeking to expand their horizons in terms of both what they are familiar with and what they are comfortable with.
Which leads to his second point. The biggest impact is not the movie/book itself, but the conversations arising from it.
I agree with both points.