You didn't mention the term, but if your notion of propaganda is something that can just infect you without warning, then it's not really in line with the scientific views of propaganda and it's much closer to the brainwashing theory. If you just scrolled reddit or listened to a Jordan Peterson lecture every day, would you really be in danger of becoming an anti-communist because of it?
The point is to reject completely any "brainwashing" theories, even if in quotes, because they are unscientific and don't really explain anything. It's about recognizing that people buy into propaganda for specific reasons, exploring those reasons, and about formulating effective strategies to get them to "buy out" if possible. It's about actively rejecting said propaganda and getting people to do the same.
That is not the claim, no one has ever claimed this. Propaganda definitely has an effect, but the way it works is different and specific, and it's possible to fight against it. Have you read the article I linked?
But you did explicitly mention, in your second comment, this:
implying that "brainwashing" can exist at least in some limited fashion. You framed your critique only in regard to brainwashing and not the actual theory I'm a proponent of (the article explicitly deals with such points and proposes how to fight them). The point is that the way propaganda works is not by some invisible ever-present influence, but by socially licensing us to go along with certain things. In the same manner marketing and advertising work as well (the ads that don't simply reveal to us use-value of a necessary products, but those that attempt to create a specific brand image).
This claim no one disagrees with, but that is not the same claim you made before. The point is that we rationally choose what we interact with and what we believe, and both of those things are underpinned by our material conditions, but it is possible to rationally make a choice against the prevailing default narrative in society.