First, let me clarify what is meant by "Thought Control". Many people believe that thought control means that a person's thoughts are controlled by some external force -- another person or group -- but that isn't the case. Thought control is that a person learns to control their own thoughts based on certain rules. It is self-imposed control over one's own thoughts.
When you start talking about Scientology's "thought control", many Scientologists get upset, "No one is controlling my thoughts, I'm the one in full control," and that is, actually, true. They are in control, but they are not free.
To become a Scientologist, you must learn to control your thoughts, and your actions, to conform to the rules and requirements of Miscavige's Church of Scientology.
Let me give one example of how this works. There are many, many ways this is done, but this example is one of the earliest learned.
As is standard in Scientology, this is a made-up word by L. Ron Hubbard. The definition of "entheta" is "enturbulated theta". "Theta" is defined as "life force". "Enturbulate" is defined, by Hubbard as "to agitate or disturb; to upset."
So "entheta" is "agitated or disturbed life force". Or, more simply, "entheta" means upsetting news, information, circumstances, etc.
In Scientology, entheta is bad. Scientologists learn that good news (or "theta") is "good" and bad news (or "entheta") is "bad". Entheta must be rejected by all loyal Scientologists -- especially "entheta" about Scientology, Dianetics, Hubbard or Miscavige. Anything upsetting must be rejected as entheta. Entheta will harm you. Entheta will interfere with your "progress up the 'Bridge to Total Freedom'!" Entheta is bad.
But notice something very, very important. The definition of "entheta" has absolutely nothing to do with what is true or what is false!
The automatic response that Scientologists have learned, that they must reject all entheta, is completely outside of truth and lies. Negative and upsetting information about Scientology, Dianetics, Hubbard and Miscavige must be rejected as entheta even if absolutely true.
And the corollary is also learned and practised by all Scientologists: Good news and information about Scientology, Dianetics, Hubbard and Miscavige must be accepted because it's "theta" even if completely false.
Of course, Scientologists are not allowed to think in terms of what might be true in any negative information or what might be lies in any good news. They may only think in terms of "entheta" and "theta".
And so, Scientologists learn to control their thoughts according to what is "entheta" and what is "theta", and not by what is true and what is false.
If a Scientologist reads or hears something about Scientology, Dianetics, Hubbard or Miscavige that upsets them, they automatically and without thought reject it as "entheta". They no longer allow themselves to think about truth and lies. It is self-imposed thought control.
It's easy once you get the basics down.