Merriam-Webster

the spreading of ideas, information, or rumor for the purpose of helping or injuring an institution, a cause, or a person

Cambridge

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

Oxford

The systematic dissemination of information, esp. in a biased or misleading way, in order to promote a particular cause or point of view, often a political agenda. Also: information disseminated in this way; the means or media by which such ideas are disseminated. Cf. black propaganda n.

Collins

Propaganda is information, often inaccurate information, that a political organization publishes or broadcasts in order to influence people.

Point being, even if it’s not necessarily all lies how do you know you’re not being lied to or mislead when most propaganda are, by definition, lies and half-truths? I don’t trust any sort of propaganda because chances are I’m being lied to.