What does “Jus’ folks is jus’ dumb” mean?

Question

I found the article titled “5 myths about Rick Perry” in today’s New York Times literally dealing with the mystery of Texas Governor who is running for 2012 GOP Presidential nominations entertaining. However I was caught up with the following lines in the article:

“He’s a hillbilly dimwit. That’s bias against Texas, pure and simple. --Don’t make the mistake of thinking that jus’ folks is jus’ dumb.”

I interpret ‘Don’t make the mistake of thinking that “jus’ folks is jus’ dumb’” means “Don’t think an average (or ordinary) person is just a dumb.’ Is my understanding correct? Is “jus’ folks is jus’ dumb’ “a proverbial expression?

I also came across my usual question about the discordance of numbers of the noun and verb in the above paragraph. Why ‘jus’ folks, which is plural in number is followed by ‘is’ and ‘a dumb,’ both in singular?

Answer 1

"Jus' folks" is a rural-American dialectical expression meaning, roughly, "plain, ordinary people."

Saying

"Don't make the mistake of thinking that jus' folks is jus' dumb"

means don't think people are stupid just because they don't speak in an educated style (so they don't appear to be very smart).

As for the disagreement in number, that is itself a hallmark of rustic speech:

We was nigh on to sunrise before the dog come home.

(Note also the use of present tense to indicate past tense in that rustic colloquialism.)

Answer 2

In both cases, "jus'" is short for "just". It's intended to mimic the dialect of "ordinary" people.

The phrase "jus' folks" is intended to refer to those same "ordinary" people.

In the phrase "jus' dumb" the "just" is an adverb meaning either "only" or "very" (or maybe both), modifying "dumb", which is being used as an adjective.

So, translated:

"Don't make the mistake of thinking that ordinary people are merely dumb."