Because they literally, not figuratively, believe that watching something makes you believe it. And that if you don't watch something or aren't exposed to something, it makes you not believe it.
They have academic gibberish to tip-toe around these points, but this is really what it is. They believe that humanity is a somehow a blank slate and we're imprinted on the world around us. This is not possible. Tabula Rasa is a circular theory. Because if we're a blank slate, we require the mechanisms for that slate to be etched upon. It doesn't mystically happen. So if we have mechanisms to write upon that slate, then we are not a blank slate. Hence tabula rasa is a logical fallacy. I don't need to be in STEM to tell you this. Philosophy 101 disproves Tabula Rasa.
Their entire philosophy and theory of the world is based upon a logical fallacy. They're basically equivalent to people thinking that if children see Superman fly, children will jump off roof-tops. Except they expand that to the whole of humanity. That's why they shove this shit into shows and everything.
The problem is the world doesn't work this way. The more people see an ideological bent all around them and look at their world and they experience a dissonance, they rebel against it. This is why you see this massive right-wing rise basically across the world. This dissonance is only prevented one way: through violence. Which is why no communist state has ever existed in the world without violent, non-democratic authoritarianism.