Is it true that all rednecks are backwards ignorant bigots?

Actually, not all those who identify themselves as "redneck" are ignorant or bigoted. Folks can surprise you.
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It depends on your definition.
In Australia, the term does have that meaning and no other - and the "bigot" part specifically includes racist.
Here, it's because many of the "white" settlers had pink or reddish skin due to being fair and flushed in the heat or sunburned. Much more common with Scotts descendents living in rural areas. Quite often their necks are literally a crimson-reddish colour in the heat.
The term "redneck" can thus be a racist term of abuse in that it assumes that all people who happen to have red necks are racist, ignorant and dull or dumb.
Naturally, appearances are no predictor of internal traits.

I believe there are several different meanings in different parts of the world. One US woman told me that, [in her area,] it just meant a working man or labourer who wore a red handkerchief around his neck.

Of course not, but the living conditions of rural areas do tend to keep people ignorant. That's why rural areas tend to vote Republican.
Which is too bad, because redneck culture is pretty fun. I almost died mudding, then chose to do it two more times.

Our necks are red cuz we're angry and we get sunburn

Don't mean we can't be mad at ignorance and bigots

...not in keeping with your name...?

I'm sure maybe one of them isn't.

Become one to find one .

Watch out for the ones with the rifle racks...😅

No, only 20 something women are.

Not necessarily, there are some cool rednecks who despite being ignorant are very nice people.

No There's some rednecks that are cool and they have friends of all stripes.

I know black rednecks that are very fond of white people so no.

Be a backwards ignorant bigot ONE TIME! and you're labeled for life..