I've believed for a long, long time now that the whole Liberal Media Conspiracy was a concoction of Nixon's, and a brilliant bit of long-term strategy. You cannot disprove the existence of a conspiracy, and by its nature, a conspiracy actively works to eliminate all proof of its existence.

Of course, "liberal" didn't really become a dirty word until the 1988 presidential campaign. Same time "card-carrying member of the ACLU" became a smear.

So today, as you observe, the press bends over backwards to avoid being accused of liberal bias. In the name of "balance", they give equal time to the round-earthers and the flat-earthers.