Propaganda doesn't totally rob people of agency free will (more accurate term), if it did this site wouldn't exist. People do have the capacity to develop critical thinking, skepticism, and a basic curiosity about the world that allow them to develop some resistance to propaganda.
You can hold people accountable for failing to even attempt to do this.
I really don't think that's the concept the OP is invoking-- consider the choice of the word develop rather than something like innately possess
I don't disagree with your criticism of the concept itself, that sort of exceptionalism as well as the view of oneself as a static, immutable essence (or defined by static, immutable characteristics) are both dangerous