I guess where we disagree is probably more at how common certain talking points become. We, as social creatures, naturally adopt the mannerisms and at least some of the outlooks of our communities - thus, sowing specific points of view in a niche community is a very cost-effective and practical way of amplifying propaganda.
Of course, as the saying goes, "You are not immune to propaganda". It's something we all must be aware of, lest we become (or remain) useful idiots ourselves.