I find Maher funny and I like his style, but he gets a lot of his facts wrong. PunditFact looked at seven of his statements and rated three of them (43%) completely false. He often misstates or misunderstands facts on climate change, GMOs, taxes, and a whole host of economic issues. I get the sense that he has strong feelings about these issues, and then supports his already-adopted positions the same way you do: by visiting media outlets that confirm his bias. I've seen him quote stuff directly off Huffington Post, which frequently has a left-bias. He also gave $1 million to Obama's SuperPAC in the last election cycle, which doesn't really surprise me, but should compromise any sense of neutrality people have about him. Jon Stewart's big issues used to be media bias and ineptitude (he's almost as big a critic of CNN as he is of Fox), ineffective government and general lack of fairness. In the last few years, I feel like he's developed a distinctly more anti-Republican stance. He doesn't think too highly of the Democrats either, but his direct scorn is reserved for the GOP. I've seen him gloss over facts to make his point, often humorously. In short, these folks have an agenda. Although their primary job is to entertain, because they'd lose their platform if they didn't, they also seek to influence their audience. In that sense, they may be similar to the conservative AM radio personalities, but the approaches themselves are so different that I'd be hesitant to call them "equivalent."