On January 15, 1836, an editor for the Newbern Spectator expressed his disapproval of the criticism being printed in the Southern Literary Messenger in Virginia. The critic was Poe, of course, and the editor referred to Poe's "unnecessary severity". Poe would earn the nickname (and accompanying reputation) as a "Tomahawk" man.
It is really as a critic that Poe first becomes a well-known figure in American letters. He popularized (I won't say "created" because that's tough to prove) a new type of literary review which was (shockingly) based on sincerity on the part of the reviewer. These honest opinions were presented even if they were negative - which likely surprised readers used to the puffery system. This system, which fellow critic Margaret Fuller later referred to as the "mutual admiration society" (specifically in reference to Boston), was always positive. In other words, reviewers only wrote positive reviews.
People like Poe (and Fuller) took issue with this because it did not push for the betterment of American writing and instead allowed poor writing to pass unchallenged. Poe broke those rules because he couldn't stand the false compliments. Reading reviews of the day, as Poe said, would convince you that "all our poets are Miltons." Poe may have been a bit over-the-top in his criticism partly to add balance to the excessive praise.
On a personal note, I will be out of town celebrating Poe's big day (and doing some personal traveling) for the next week or so. If things are quiet on this blog it's because I've become too entranced in real-life Poe to spend time in my digital Poe world. My apologies in advance!