China and the Soviets are practical examples to the contrary. Even the current information war inside America is an example of how critical freedom of speech is to the freedom of thought. Not only is it essential for most people to recognize they are not alone in a thought/sentiment, control over information constrains the information thoughts can act on.
If you never hear about problems, how do you solve them? If you are only ever showed information that is favorable to a group - how are you to arrive at some realization, sans their incompetence, that things are not as they are presented?
The freedom of thought is irrelevant. "The Party" doesn't care what you think, they care what you will say and do. How you rationalize service to it is irrelevant in the civic context.