http://www.latimes.com/news/politics/la-na-onthemedia27-2008jul27,0,712999.story Haters of the mainstream media reheated a bit of conventional wisdom last week. Barack Obama, they said, was getting a free ride from those insufferable liberals. ... The Center for Media and Public Affairs at George Mason University, where researchers have tracked network news content for two decades, found that ABC, NBC and CBS were tougher on Obama than on Republican John McCain during the first six weeks of the general-election campaign. ... During the evening news, the majority of statements from reporters and anchors on all three networks are neutral, the center found. And when network news people ventured opinions in recent weeks, 28% of the statements were positive for Obama and 72% negative. Network reporting also tilted against McCain, but far less dramatically, with 43% of the statements positive and 57% negative, according to the Washington-based media center.