I take their meaning as a poke at those who believe that "if you will it, it will be." There were some who believe(d) if you gathered a stadium of people and told them all to think about the candle in the center of the stadium self-igniting that through the power of shared belief it would. If this were true, then, to op's point, a bunch of reality would be changing to match people's mental expectations as influenced through media tropes. And since we don't see that, then people's thoughts likely don't influence reality.