Biased Journalists to Be Blamed for Media Bias?

This entertaining YouTube clip (which I am having difficulty embedding here) speaks about media bias and discusses some of the reasons why it occurs and why it's not going to stop. We raised some of these points in class, such as the fact that TV networks want money and let the business aspect drive their "balanced" views, and that extremist news show hosts do what they do because it gets them more viewers. A point that he brings up that I don't think we spoke about so much is the fact that journalists are generally liberal. They feel they have to prove their side of things and win everyone over to that opinion, so they are the ones getting involved in journalism and adulterating the news to have a liberal slant. Do you agree? Are journalists generally liberal and agenda driven?