Not all propaganda is deceptive.

The best propaganda is 100% true and still achieves it's goal.

Even deceptive propaganda isn't necessarily bad. Objectively speaking, the best thing to do for yourself would have been to dodge the draft in WWII for example.

So, the term is mainly used to convey an author's opinion on the subject of the topic and not necessarily related to the topic itself ?

Propaganda is deceptive or misleading by definition.

What definition is that?

Merriam-Webster: "the spreading of ideas, information, or rumor for the purpose of helping or injuring an institution, a cause, or a person" and "ideas, facts, or allegations spread deliberately to further one's cause or to damage an opposing cause" [1]

Cambridge Dictionary: "information, ideas, opinions, or images, often only giving one part of an argument, that are broadcast, published, or in some other way spread with the intention of influencing people's opinions" [2]

Wikipedia (quoting Encyclopedia Britannica): "Propaganda is communication that is primarily used to influence or persuade an audience to further an agenda, which may not be objective and may be selectively presenting facts to encourage a particular synthesis or perception, or using loaded language to produce an emotional rather than a rational response to the information that is being presented." [3]

Wikipedia further quotes NATO's 2011 guidance for military public affairs definition: "information, ideas, doctrines, or special appeals disseminated to influence the opinion, emotions, attitudes, or behaviour of any specified group in order to benefit the sponsor, either directly or indirectly" [4]

I think that OP's use of the word is well in line with each of those definitions.

[1] https://www.merriam-webster.com/dictionary/propaganda

[2] https://dictionary.cambridge.org/dictionary/english/propagan...

[3] https://en.wikipedia.org/wiki/Propaganda

[4] https://en.wikipedia.org/wiki/Propaganda#Definitions

I stand corrected. I should have checked the definition before making that claim. Thanks for elucidating that for me. I've understood propaganda to be one thing for nearly 30 years somehow.

You can deceive while telling the truth, like this ad from a Brazilian newspaper (dubbed in English) https://www.youtube.com/watch?v=PShbxd42JN8

Truth needs to be put in context. Truth needs to be interpreted. There is no such thing as objective truth.

Effective propaganda is like a filter that is everywhere you look. You don't know it's there because you never see the world without it.