Do you think free thinking is an illusion?

I did not know how to phrase this question but it keeps coming into my mind how powerful propaganda is and how easy it is to brainwash people with the right methods. I know normal people that completely lost themselves in conspiracies and Russian propaganda and even marriages that failed because one person completely brainwashed himself.

Like in Nazi Germany a whole country (at least most of it) was taken by conspiracies and after the US took over in the West they did control the media strictly in order to "denazify" the population and any criticism on the occupation wasn't allowed. They did not allow any Soviet propaganda neither. Until today you are not allowed to question the holocaust (some conspiracies do) or display any Nazi symbols. All this in order to basically protect the people from themselves and it did work.

We do know today that Russia works hard to influence elections and far right parties use social media to basically brainwash people into dangerous beliefs.

How safe is it to just let people filter out any information? History shows that free thinking is not so free after all and that the masses can be manipulated easily.

On the other hand to let people freely chose what media to consume and build their own opinion is such a sacred basic right that it should not be restricted.

Do you think there need to be safety measures to protect people from being brainwashed or do you think that would take away the basic freedom people and would set a dangerous example?