Like so many other wonderful Chomsky insights, it helps to explain quite a bit about the mechanics of political discussion:
What makes this quote particularly relevant right now is the impeachment hearings, in which one can observe a "lively debate" on narrowly focused topics such as (1) should the senate call witnesses? and (2) should there be documentary evidence collected and submitted for review?
The debates do give the sense that there's some free thinking going on, but in reality, there's no thinking at all. There are first-hand witnesses that could clarify exactly what happened. There are first-hand emails, texts, and recordings that could clarify exactly what happened. There are witnesses that are practically throwing themselves at congress to testify. It's entirely possible for the American people to understand what really went down, as far as it relates to potential impeachment ... but nobody is ever going to debate that subject, because all of the "lively debate" is to whether to allow witnessed and evidence all.
I also read an interesting [and highly related] quote about the impeachment trial recently:
Judging from CSPAN, one might rightly conclude that the US Government is functioning. Clearly, it is not.
If no evidence is reviewed, there will be no debate on such highly germane topics such as (1) is whatever Trump did impeachable? (2) why did Trump issue a unilateral order to ignore all subpoenas (is that considered obstruction?) (3) is tying every subpoena up endless litigation a good precedent for future presidents (or is there a better solution to allow for legal contesting of these without waiting 18 months for a resolution?) (4) is it considered obstruction to say "Honestly, we have all the material"? (5) why is every defense a procedural objection instead of an actual defense? (6) are some GOP congressmen involved in the impeachment proceedings actually involved in the scandal itself?
(if there was evidence and/or witnesses, we could very well answer those questions)
Oh - and before I forget - here's a bonus Chomsky quote .. it's a great one: