Isn’t propaganda just a form of persuasion? What about propaganda separates it from advertising or interpersonal communication?
Edit: Not all propaganda involves lying. For some reason, we seem to be more comfortable with a person lying to us than we are with viewing a propaganda poster that uses verifiable facts.
Edit 2: Another interesting note is that in some countries, propaganda is not viewed negatively like it is in English speaking countries.
To me I think it has to do with propaganda being dishonest about being propaganda. Regardless of whether or not the content is disingenuous, propaganda often is presented as not propaganda, and that sets people up to have a bad impression right from the get-go.