What makes the Sydney barber's remark rude?

Question

In Banjo Paterson's poem "The Man from Ironbark", a city barber makes a supposedly rude remark to his country bumpkin customer:

And as he soaped and rubbed it in he made a rude remark:
"I s'pose the flats is pretty green up there in Ironbark."

It's not clear to me what makes this rude.

I can imagine that the general idea is simply that country folk are naive ("green") - but that would seem to require "flats" to in some way represent those people, a connotation I'm unaware of.

I've also seen it suggested that it's a kind of taunting, ironic remark about the generally dry conditions in the outback, or even a specific drought, such that the local river flats would in fact not be green at all. But that seems pretty obtuse, and would seem to require knowledge on the part of the reader about conditions in that part of the country at the time. I guess we can't rule that out - Paterson certainly wrote for his time and place - but it does seem a stretch.

Or maybe I'm misinterpreting what's meant by "rude" in this context?

Answer 1

This is straightforward with the assistance of a comprehensive dictionary:

flat, n. 21. (obsolete) A dull fellow; a simpleton.

green, adj. 7. (figurative, of people) Naive or unaware of obvious facts.

_{Wiktionary (flat, green).}

We have to suppose that, at the time the story takes place, these senses were slangy enough that the city barber could be confident that his country customer would not know what he meant by them, and would interpret them in the following innocent senses:

flat, n. 1. An area of level ground.

green, adj. 1. = verdant, adj. 2. Lush with vegetation.

_{Wiktionary (flat, green, verdant).}