If you want credibility, you must earn it. What is a reputable, authoritative source? What are the characteristics of a source which can be believed as accurate?
An authoritative source is strong on multiple fronts, none of them being the opinion or statement of a single entity.
Vet your sources. “Vetting” means finding its source of authority.
If a source comes from an objective panel of proven, established experts without bias, it is authoritative.
If it comes from direct evaluation by objective professionals without bias, it is authoritative.
If it comes from stringent objective international evaluation without bias, it is credible.
See the key factor, here?
If propaganda comes from a SUBJECTIVE, BIASED source, plain and simple, you should question every statement that source makes, and compare it to every OTHER relevant source you can find. It is important to branch out. OBJECTIVITY is the basis of all science.
If it comes from anyone with something to gain from your support, keep looking; it is not authoritative. Loud, maybe. Fancy, why not. It may be insistent about itself and its power and its rightness and correctness and invincibility, but does that make it credible? Keep looking, because none of those traits translate to credibility. If they did, Trump saying he won the election would make it so.
Think about it.
Do not allow yourself to be manipulated.