> You cannot control peoples thoughts by reducing their exposure to the bad thoughts.

Actually, yes, you can, quite literally. Falsehoods repeated ad nauseam are convincing in the long run (do you remember the second Irak war and the WMD hoax propagated by the government? Half the US still believes that one).

In a meeting, a single person making the same argument three times is almost as convincing as three people making it once.

Etc...

We're not as free as you imagine.