That's probably why the title of the essay is "Persuade xor Discover". pg started out thinking about Arrington, but, since he was writing to discover, he explored other ideas. Those ideas became the main point of the essay.
pg cites his own curt/succint approach to writing as a reason people dislike him and speculates that people dislike Arrington for the same reason, thus using Arrington as an example for part of his argument. While pg's central thesis in the essay stands, the Arrington example does not.