News in that era was "unbiased" mostly because the US government had a soft censorship regime in the form of the FCC and corporate ownership of TV spectrum. Walter Kronkite calling out the government on Vietnam was the exception rather than the norm. What people are remembering isn't "objectivity", it's one particular bias[0] everyone was required to have in journalism - i.e. the illusion of objectivity.

Today's "biased" news is just regression to the American mean. When people got their news from newspapers, almost a century ago, you had similar levels of editorialization, bias, closed-mindedness, clickbait, misinformation, and so on. The "unbiased" era was largely a product of technical limitations that went away with cable, and later the Internet.

[0] Or, more specifically, what Noam Chomsky called the "five filters". See: https://en.wikipedia.org/wiki/Propaganda_model