Yes, the right wing has gone after the legitimacy of the mainstream press for years. No I don't agree that the political press has a liberal bias if by "liberal bias" you mean in any consistent way furthering some sort of liberal agenda. Sure I buy that in general reporters are a bit more liberal than average on some issues (mostly not on economic or foreign policy issues) in the abstract, but that rarely manifests itself in concrete ways, and for mysterious reasons many of the most prominent mainstream media voices aren't liberal at all. Even on the issues that the press tends to be "liberal" about, they tend not to be all that interested in government solutions to those issues, so it's a largely ineffective liberalism. It's a bit like academia in that way.
The maddening thing was that when The Left started our little grassroots media criticism endeavor, members of the press loved to perceive criticism as just two sides of the same coin. Both Sides were just working the refs, and if you were pissing Both Sides off then you must be doing something right! But liberal media criticism really never was that way (I think there's a bit more of that than there used to be), simply press criticism as one more political tool. We didn't want to de-legitimize the press, we wanted it to be better. And, yes, we wanted them to stop listening to bullshit rightwing criticisms and chasing every Democratic scandal/slanting every story in order to please Limbaugh listeners. Given the decades of much more effective right wing criticism of the press, along with certain management pressures, even Both Sides has never been Both Sides. It's at best Both Sides most of the time. You know, when Bush was in power Republicans needed to get their voices out because they were in charge. Then it was only fair to give the opposition more time. That's how Both Sides has operated, in a strangely one-sided fashion.
As we tried to tell them, The Right will hate you no matter what you do or how many of them get columns and teevee shows and permanent offices at Meet the Press. And here we are.