Working through the haze of media manipulation is an extremely complex task. It requires a ton of interest, time, effort education, IQ and mental discipline. Most people don't have a chance to resist society-wide campaign of lies; they're absurdly outmatched.
This is the same reason we have enforced pension plans, etc. You could just say people should save their own money. That would work fine for me and you. But most people just don't have the mental context to delay gratification that long. Their brains are not adapted and not equipped for the modern world.
So it's wrong to feed them socially-destructive lies, for the same reason it's wrong to feed a dog well-labeled poisonous meat.