I really don't know when that was. Walter Cronkite? What a laugh. Maybe Huntley-Brinkley, when you consider Brinkley's famed late-night outburst at Clinton's re-election.If conservatives existed in the networks (Hume at ABC ?), they policed themselves to objectivity, likely due to their values or wanting to retain their employment.
Edward R. Murrow trashed Joe McCarthy. The media lauded Kennedy, trashed anti-communists, and agitated for left wing causes even when I was a child, which was a long time ago. They just got their way for so long, we never noticed their true bias until Reagan, when they acted like a cross between screeching pigs and whining kindergartners.