The whole discussion of "art" falls into the same catagory as this I believe.
Probably, a great photograph like any great art, has to evoke an emotional response.
The greater the response, perhaps the greater the art. ALso the response does not have to be shock, or discomfort.
A peaceful scene can also evoke a wonderful response.
To a photographer a picture of Westons still life may evoke an emotional response of admiration for technique, where to the public it may not.
I believe the MM shot was a great picture and representative of the breaking out of the "morally stagnant" fifties. Interesting how tame it seems today. Also it was an early picture of an ikon, and a marketing tool of an industry. A girl who sold her soul for what she thought would make her happy and tragically it never did.