Funny news is good news
Mike Vassar pointed out to me that he gets better news from humorous sources such as The Onion, The Daily Show, and the Katrina: The Gathering
Magic deck, than he does from newspapers and network news. His theory, transmogrified through one late-night conversation on a bad cell phone and a few days of bouncing around my head, is that humor relies on suprise, and surprise relies on conveying information, whereas ordinary news can invoke other addictive emotional affects without conveying information. Hence, humorous news tends to be more information-dense than regular news.
Some other reasons could be Professional political newscasters care deeply about politics, and take sides passionately, and so can't present news objectively. Comedy is aimed at a general rather than a partisian audience. Many humorists take potshots at everybody, regardless of party affiliation. Professional news is more closely monitored by the network to ensure it says nothing that conflicts with the network's, or the network's owners', political interests.