To borrow your framing, collectively internal filters will manifest as emergent external filters. It can be considered emergent/systemic propaganda. Even the freest societies fall victims to this.

That's not at all to say we're doomed to be brainwashed; along what you're saying, with conscious awareness, effort, openness to reassess, and honesty (first and foremost to oneself) we can better ourselves and the social groups we're each part of.