Historical Research: Facts vs Propaganda

Propaganda:

Any systematic, widespread dissemination or promotion of particular ideas, doctrines, practices, etc. to further one's own cause or to damage an opposing one.
Webster New Dictionary.

Evaluating Sources
Among the many sources a researcher comes across, there is also propaganda. Sometimes he/she is not aware a document is propaganda until after a lot of double-checking.
The propaganda source looks good and sounds true.

The researcher has two choices.
1) set it aside with a stand thee behind me shrug
2) keep it.

Determine Value Of The Propaganda Source
Depending on the author's storyboard, the propaganda source has value or it has none.
Because it is a propaganda source, it does not mean the researcher cannot use it.

Examples:

1) Viet Nam Era: Hanoi Hannah
Author # 1 is researching the Viet Nam era... The hero is a young farm boy from the Corn Belt. He joins the army and goes to war.
During the Viet Nam war, a woman called Hanoi Hannah broadcasted propaganda aimed at the G.I.s.
All soldiers heard Hannah, at least once, during their tour of duty. Everyone knew it was propaganda.
Hanoi Hannah and her broadcasts existed, and were part of the Viet Nam War era.

If the author uses one of Hanoi Hannah's transcripts in his novel to portray the life of a soldier during the war, the propaganda source is valid. It is valid because the author does not use it as proof, but as a means to portray the era.

2) WW2: Nazi Propaganda
Author #2 is writing a book on WW2.
While researching, he finds a 1944 Nazi pamphlet (Caught like Foxes in a Trap). This propaganda wanted to make the G.I. believe the V-1 rocket would turn the tide of the war. On the flip side of the pamphlet were a series of quotes from the Foreign Press confirming this point of view.
We all know this did not happen.
Let's imagine our author doesn't know this.
If the author uses this propaganda source to prove the V-1 changed the tide of the war, it is not valid. It is not valid because he is trying to prove an event which did not take place.