The ideal function of propaganda is to win popular support for a cause by captivating the emotions and flattering the reason of the public. (i.e. men llke to think that they are acting according to reason even if in reality emotion and other non-rational forces are, as so often, much stronger determinants). Popular propaganda should subtitute emotion for reason under the guise of facilitating the process of reasoning.
Propaganda is a machine for generating and maintaining enthusiasm. Propaganda should therefore:
i) never be dull.

ii) never be offensive to its audience.

Intellectual reasoning should be as objective as possible. Propaganda is, by its very nature, subjective. It is subjective because:
(i) A specific object (e.g. national victory in a war) should inform all its arguments, methods of presentation, etc.

(ii) Propaganda should appeal largely to non-rational elements which are more susceptible to subjective than to objective influence. (e.g. Issues should be presented in personalized form as far as possible). The subjective approach usually has greater dramatic appeal than the objective.
https://medium.com/@thegrugq/british-memo-on-propaganda-1939-7cc08d40897