I have always found myself in a difficult mental position (would a modern writer have written space?) regarding Arbus.
My initial reaction, insofar as I can remember it, was of revulsion and a sense of yuck! how could she want to do that? Later, when my career was a thing of the past and I began to play around with it (photography) for its own sake, I wondered if I could get myself interested in the HC-B and early Klein things, not as objects of veneration and/or admiration, but as something to do, that would cost nothing, yet let me keep actively engaged with the medium... All too quickly I realized that I lacked both the city culture as well as the cojones to stick a camera into somebody's face and shoot 'em dead in the street. Instead, my focus became altogether more restrained and possibly introverted - atavistic, then, since it was the relative unreality of my model photography work that created the ambience in which to be somebody else - for both parties, I believe...
That made Arbus even more of a mystery for me, because I couldn't help compare her set of balls with my own lack of a large enough pair for the street job. Whether or not her fragilty was a stronger weapon than the testes of Atlas I don't know - possibly, it really was, and pictures of her carting around a huge Mamiya TLR and an even bigger flash unit make her look anything but the predator she probably was. She was unavoidably just so in-your-face that she may even have given some the impression of being a sort of "official", government-sponsored professional just doing her job, and thus not some private person with a strangely intrusive interest and agenda. At least, in public spaces such as parks and, even on streets, this could have worked for her.
Non of which gets into the reasons why she did what she did. Perhaps the only way we can do that, is by confronting our own emotional responses to her subjects, but then that would only apply to her pictures of people with no name. The minute that the subject becomes somebody such as Greer, the rules shift, and she is working on a project that carries the expectation of exposure where it may count - though having dumped a career with one of the top fashion rags, that proposition and supposition about her needs or motivation may not really stand - and so is a work on Greer the same deal as with the gigantic son within the relative doll's house? Either way one looks, the mindset of the woman becomes more unclear and perhaps that should give us the clue.
In conclusion, I can only know that I would not want to do the same work as did she; that I have a sense of admiration for whatever drove her spirit (or was it destroying it, instead?), and that in general, I wonder if she was actually playing with a full deck. And there yet another catch: is any of us equipped with the full fifty-two?
I think she will for ever remain the photographic enigma she has always been.