He doesn't have to -- he's making the point that many professional photographers swear by full-frame DSLRs, but there are people who would treat that with the exact same dismissal that you applied towards iPhone photos.
The implication is that it's no more "ridiculous" to read articles about professional photographers using iPhones for their rarely-used macro shots than it is to read comments from people who find the idea of using phone cameras for this purpose laughable.
The implication is that it's no more "ridiculous" to read articles about professional photographers using iPhones for their rarely-used macro shots than it is to read comments from people who find the idea of using phone cameras for this purpose laughable.