…, the forces responsible for, and senior to, the Mai Li massacre, …
…, the general civilian population voting for the explicitly racist Nazi party, …
Why? Because these things only happened as a result of the fact that speech is convincing.
Best you can do here is say "those people are not well-adjusted", which is fine except for where the mal-adjustments come from: speech.
Think about it in reverse: if speech had no power to change us, it would not even matter if it was free or not.
The benefits and dangers of free speech are two sides of the same coin: the capacity to convince others to act in accordance with your beliefs.
"Well adjusted adults" as a phrase can only point to those who are within the Overton Window of their society, regardless of whether that society calls for things I condemn, or not.
This means that well-adjusted adults can, will, and have, formed lynch mobs upon hearing rumours that someone has eaten beef.
To be more clear, these regimes arose because of the lack of freedom of speech, not because of the excess of it.