They’ve always been libs but they appear more biased today and back in 60s/70s there were a few anchors ....newsreaders....not as flagrant
The Left then of which I was admittedly pretty much a member hated the alphabet networks and print media and found them not lefty enough
The left today and most of the media and Hollywood and Internet tech are fellow travelers
They view Rachel Maddow and Van Jones and Don Lemon as peers and contemporaries
Plus the network owners like Paley and especially Sarnoff were not lefties per se
Sarnoff was a serious righty and Paley knew the limits like the Howard K Smith affair
Walter Cronkite CBS and Chet Huntley NBC were very much on the Left, but it wasn’t as blatant as what we see today. It was done more through story selection, what they chose to report or to ignore. Arnaud de Borchgrave novelized that practice in ‘The Spike’. David Brinkley NBC provided some balance. I can’t recall who anchored ABC back then, maybe Howard K Smith.
And of course there was the pervasive moral preening associated with the Northeastern position on the Civil Rights and antiwar movement.