one need not take cognisance of anyone else's opinions or group norms, but one can simply decide for oneself what is important and meaningful
That's not what I read into it.
A question you should consider, one of the yardsticks by which to measure or test a belief ('doctrine', 'quality', or 'behaviour') is whether it is "praised by the wise" and "blameless".
It also states several bits of Buddhist doctrine as self-evident, for example ...
When greed arises in a person ... it arises for harm not for welfare"
... and/or axiomatic, for example ...
"And this greedy person, overcome by greed, his mind possessed by greed, kills living beings, takes what is not given, goes after another person's wife, tells lies, and induces others to do likewise, all of which is for long-term harm & suffering"
I think that if what you "simply decide for yourself" contradicts these (Buddhist) axioms then I don't see such a decision as being supported by the sutta.
Instead I think it's saying that if you practice the (Buddha's) doctrine then you will experience (i.e. "know for yourself") the result (and that the result will be a better result).
I find it more prescriptive than permissive, for example ...
One who is a disciple of the noble ones — his mind thus free from hostility, free from ill will, undefiled, & pure — acquires four assurances in the here-&-now
... is prescribing a "mind thus free from hostility".
Is The Kālāma Sutta Really Libertarian?
I found this page on fakebuddhaquotes which gives what the author describes as a "libertarian" interpretation of the sutta ...
Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense.
... and which it says is ...
... is a bad translation of the Kalama Sutta — so bad, in fact, that it contradicts the message of the sutta, which says that reason and common sense are not sufficient for ascertaining the truth.
His view of the sutta is,
The Buddha’s reply is very full, but it’s clear he says that “reason” (logical conjecture, inference, analogies, agreement through pondering views) and “common sense” (probability) are not sufficient bases for determining what the truth is. It’s not that these things should be discarded, but ultimately it’s experience and the opinion of the wise that is our guide.
Further to that ...
Now you don’t have to take everything they say as being the absolute truth. You can use your reason, your common sense, and your experience as a guide. Not all of “the wise” will agree, for example, so you’re still going to have to figure things out for yourself ultimately.
Still he claims that the criterion that "the opinion of the wise should be a guide" is often overlooked, and he describes this (overlooking this criterion) as a "libertarian" position.
IOW (to answer your question) I think the author believes that the sutta isn't really "libertarian" in that sense.
a political philosophy that upholds liberty as its principal objective
Well that might have a parallel in Buddhism, for example The Taste of Freedom,
As though in response to mankind's call for wider frontiers of freedom, the Buddha offers to the world His Teaching, the Dhamma, as a pathway to liberation as applicable today as it was when first proclaimed twenty-five centuries ago.
"Just as in the great ocean there is but one taste — the taste of salt — so in this Doctrine and Discipline (dhammavinaya) there is but one taste — the taste of freedom": with these words the Buddha vouches for the emancipating quality of His doctrine.
Or for example the word ananta (endless, limitless, infinite) was mentioned in another topic that people were discussing recently.
However that's not the same interpretation of "liberty" as various modern versions of 'libertarian' some of which say (if I'm not misrepresenting them) for example that people are well-advised to arm themselves in order to be able to defend their own property with lethal violence.
If you're looking for a parallel outside Buddhism, I know hardly nothing about schools of politics or philosophy but I'd guess that Buddhism might be closer to stoicism than libertarianism; in that for example something like this sounds Buddhist to me,
The Stoics taught that destructive emotions resulted from errors in judgment, and that a sage, or person of "moral and intellectual perfection", would not suffer such emotions.
In terms of "freedom", it doesn't mean (doesn't teach) freedom to have destructive emotions (and/or behaviours): what it's teaching is freedom from destructive emotions.
Why do people read the negative criteria as referring to test beliefs?
You're saying it's about behaviour not belief, i.e. it's about "making decisions about how to behave".
I see that as a "belief" for these reasons:
In the translation I'm using the Kalamas start with,
They expound & glorify their own doctrines etc.
The question then is about "doctrine" which I equate with "belief" (even when the subject of the belief is "how to behave").
The Buddha asks them,
What do you think, Kalamas? When greed arises etc.
I'm equating that question "what do you think" with a question about belief, i.e. "what do you believe?"
The subject of the Buddha's questions is the three unwholesome roots, and I think he's saying "Buddhist doctrine is that these are unwholesome" and is asking various questions about this doctrine:
- Do you believe this doctrine? Given that you do ...
- Do the wise agree with this doctrine? And ...
- If you practice this doctrine does it lead to welfare?
So again it's talking about doctrine, for example the belief that greed is an unwholesome root.
I equate 'belief' with 'view'; Wikipedia's description of right view suggests that it,
... acts as the reasoning with which someone starts practicing the path. Right view gives direction and efficacy to the other seven path factors.
So behaviour is important, but perhaps action proceeds from view, i.e. you behave a certain way because you have a view (or belief) about behaviour and about how to train your behaviour.