Just watched this minutes ago on The Crown on Netflix. Interesting that they made it so political even back then.
I see it constantly among people that have little exposure to actual historical documents.
I suspect its origin is a bit of nostalgia for the "simpler times" of the past and the often horrendously bad methods many people learn history.
Often history is presented as a cleaned up and certain narrative - At simplest, a history of events that happen on dates. They often leave out the machinations, plotting, betrayals, and intrigue that was almost always present.
We strip the messy humanity from history as we build simplistic narratives.
Looking back it may seem to be obvious that Nazis should not have been appeased, but at the time there were many intelligent and informed people who thought otherwise. Same with the US getting involved in the War.
Politics have been a thing as far back as we have written records.
Only thing I'd add is that the written historical record only tells part of the story and can often get amazing insights from other sources such as the material record (i.e. archaeology).
US Revolutionary war papers make current day talk radio seem balanced!
Most people refer to his time period as the golden age of news, and I don't think many people realize that reporters of that era took politicized stands. He was actively against McCarthy for example.
One thing that is different is he was always fair. Ensuring he gave adequate time to the other side - and taking people of substance from that side. In the case of McCarthy he gave him an entire episode (which McCarthy wasted).