He's wrong because the Rally to Restore Sanity and/or Fear was clearly an answer to Glenn Beck's Rally, right down to the name (Beck's was the Rally to Restore Honor.)
And Beck is clearly Jon Stewart's bete noir - the fact that he's done at least four parody segments of Glenn Beck on The Daily Show - and Stewart almost never steps out of his "news host" schtick - makes that quite clear.
Certainly the right-wingers think that the Stewart rally was liberal, that's why they use any excuse to attack it as Roy Edroso points out.
And even Maher himself acknowledges the opposition, when he gloats that the Stewart rally was twice as big as the Glenn Beck rally.
No, the Sanity Rally is what is known as a "dog-whistle" - we all know that "Sanity" means opposed to the Tea Party craziness. Krugman discusses the dog-whistle phenomenon and complains that Obama is not only bad at using the dog-whistle, he's actually anti-dog whistling.
I would say that Stewart and Colbert are good at dog-whistling. Even though they attacked the media explicitly, they are by no means condoning false equivalency - Stewart said so in his immortal gospel number response to Bernie Goldberg :
You like to pretend, Bernie Goldberg, that the relentless conservative activism Fox News is the equivalent of the disorganized liberal influence you find on NBC, ABC and CBS. Fox News, you may be able to detect a liberal pathogen in their blood stream, however faint. But Fox News is such a crazed overreaction to that threat. You’re like an auto-immune disorder. I’m not saying that the virus doesn’t exist in some small quantity. But you’re producing way too many antibodies.
And he also recently congratulated Chris Wallace for the Republican electoral wins, commented something along the same lines, that Fox is much more disciplined and on-message than any other "news" organization.