C-Span seemed to be the one media form that couldn't be messed with too much because it pretty much let the cameras catch it as it happened. At least that was my understanding.
The specific criticism that I heard was that when they took calls, they had one line for libs and one for conservatives, thus ensuring that both sides were heard. Ann Coulter said that there are many more conservative viewers than liberals so balancing out the phone lines unfairly gave the liberals a bigger voice.
In what other way has C-Span become a tool of the libs?