The author's point may have been valid 30-40 years ago. Now, national security apparatus dominates pretty much all arms of the government and the so called journalists carry water for them. In fact, publications like NYT actively doxx leakers if they do not align with their ideology. Corporate media journalists cannot be trusted anymore.
No whistle blower with information that damages the national security establishment will feel safe going to go to a mainstream journalist now. Therefore, we need more of Assange.