Reporters at the major outlets are almost entirely liberal on cultural issues. See the coverage of the gay marriage ruling, where the Supreme Court stretched the language of the Constitution to find that states couldn’t limit marriage to heterosexual couples. The country seems to be split evenly on gay marriage, but the major media are nearly unanimous. I don’t think this is really a matter of debate. In 2013, the Washington Post’s ombudsman basically admitted as much, with even more revealing comments by anonymous Post reporters placing Christian teaching on marriage on the same level as racism.
You see it with abortion, too, where journalists always ask difficult abortion questions of pro-life politicians, and nearly never ask difficult abortion questions of pro-choice politicians.
But it’s also true on questions of regulation, government spending and taxation. (I should add the media also has a very strong bias, which is neither liberal nor conservative, towards deficit reduction, which most journalists don’t realize is a bias.) I could give a thousand examples, but one good one was from the New York Times reporter, Jonathan Weisman, who spent the most time on the Export-Import Bank at the time, making it clear he was totally unaware about conservatives’ and libertarians’ economic arguments against export subsidies, while he was well versed in the talking points of industry and the liberals.