When the media gets pressure from only one side, they will yield to that pressure.
The left and the mainstream have fought many battles since the fifties.
I would like to suggest that the split is not between right and left but between the faith-based and reality-based communities.
When the right attacks the liberal media, what it is really attacking is objective media, with fact-checking.
Fog Facts: Searching for Truth in the Land of Spin
by Larry Beinhart
http://books.google.co.jp/books?id=8NiiHYvuTHQC&pg=PA180&lpg=PA180