The Kalama Sutta is the single sutta in which the Buddha seems to suggest that it doesn’t matter if one believes in rebirth or not - it would still be good to liberate the mind.
I don’t want to discuss the typical epistemological or philosophical implications but more structural ones.
First of all the name of the sutta is not kālāma sutta but kesamuttisutta. Kesa means hair, mutti means release/freedom.
The sutta begins with the declaration of the Kalamas about anonymous “some ascetics and brahmins who come to Kesamutta” and that their teachings confuse them.
What do we get to know about these teachers’ teaching? Only at the end of the sutta the Buddha says: “If it turns out there is another world, and good and bad deeds have a result…” and “If it turns out there is no other world, and good and bad deeds don’t have a result”. In other words he says “Even if there is no rebirth and kamma…”
But as it became more acknowledged recently, in Magadha and Kosala it was the common understanding that karmic retribution and rebirth are real. So who would at all have a teaching of non-kamma of non-rebirth?
There is only one prominent sectarian teacher with such a dhamma in these exact words: It is Ajita Kesakambali (as mentioned in DN 2).
Based on that the Kalamas were not confused by “some ascetics and brahmins”, but by Ajita Kesakambali. I would even go further and say that the name of the village could be related. “Kesamutti” could mean “Freed by Kesa(kambali)”.
In any case, the audience would be lay people who hold fundamentally diffierent beliefs than the Buddha (and most other setarian teachers). What kind of teaching would such an audience get? A teaching about nibbana? The gradual training? Most probably not. Keep in mind that Anāthapiṇḍika got the higher teaching only on his death bed (MN 143). See also other suttas in which only gifted individual lay people got the teaching of liberation (AN 8.12, AN 8.21, AN 8.22, MN 56, MN 91, DN 3, DN 5, DN 14).
So if higher teaching depended on the spiritual maturity of individuals it seems very unlikely that the Buddha would teach liberation (or brahmaviharas) to an entire village population which seems not ready/mature at all. We would rather expect a teaching on sila, basic ethics. And this is exactly what we get in the first half of the sutta.
Then there is a cut and suddenly the text continues with “Then that noble disciple (ariyasāvaka),”. Which noble disciple?! Look it up, he was not introduced before, there was no mention of noble ones or monastics at all before. To me, this is a clear insertion that was not originally there. And it is in this insertion that the brahmaviharas are taught.
My suggestion in summary is that there was a village whose main dhamma teacher was Ajita Kesakambali, who in contrast to most other important teachers claimed that kamma and rebirth don’t exist. Probably other teachers already tried to convince the Kalamas of their version of kamma and rebirth. But in the end it was the Buddha who convinced them of the relevance of ethical behavior, and maybe of rebirth too.