An aside, notice the trick I mentioned earlier. The author of that paper makes the absurd statement that one cannot separate the experience of the desert from the experience of Sommer's photos of the desert. Then he shows us artists meeting Sommer and seeing the desert. Finally, he concludes that any influence from this event is due to Sommer, not the desert. It's quite a clever way to argue for a greater influence, but it's fallacious.
I thought Nancy Newhall's remarks were spot on.
That said, Beaumont was quite a bad historian. His efforts to make Emerson out to be important are misplaced. Also, it is worth noting, ineffective. Nobody thinks Emerson was particularly important, because he didn't actually influence anyone. Given that Newhall was unable to raise a minor figure up, I am doubtful about an argument that he cast a major one down.
Otherwise, I quite liked the paper.