At least for me, I emphasize the distinction between being 'on the side of the monkey' and 'of the opinion that the law does not cover this photograph'.
In terms of desirable outcome, I think the photographer got screwed. His effort in slogging a bunch of fancy kit to the pestilent edge of nowhere is also the sort of activity that copyrights are supposed to provide an economic incentive for. Guy deserves it about a zillion times more than another few decades of Steamboat Willie. In this case the law fails to provide the incentive that would be desirable and that it was written with the intent of providing; and I'd prefer it if he could get his money for this one.
However, given his (original, before he changed it in response to the copyright fluff) description of how the photograph occurred and my best attempt at interpretation of the relevant US law; I cannot fit him in and cannot endorse any 'elasticity' in the application of an already fairly vague and broad law.
(I'm not going to copy-pasta the gory details; but if anyone actually cares about the details of my position they are here in a prior thread on the matter.)
Had he never mentioned the issue, or provided even the thinnest tissue of 'My experiment to see if monkeys will take pictures', I would severely distrust an attack along this line; I'm inclined to presume human authorial intention and to place the burden of proving otherwise on the attacker; but in this (unusual) case the photographer explicitly disclaimed authorial intention, and applying the law as I feel it should work out, rather than as it is, is a dodgy business.