I’ve had similar experiences at Bluegrass Music Festivals in the mid-Atlantic States area.
So it’s not just Southern. (Bluegrass Music is IMHO as much “Mountain” as Southern.)
And the music is from “Border” States where folks fought on BOTH sides in The War Between the States / Civil War (Take your pick).

Rural/small town narrow-mindedness maybe.
Not used to mixing with folks from a wider area or folks that are “strangers”.
Add drink and (don’t) stir.
“We’re us – and you’re not.”

Not to paint with too broad a brush -- there are also thankfully many friendly and accepting folks.

But there are some other kinds of folks too and you can’t fight them all -- especially not a gang of them at the same time.
Good way to get hurt.

Odd since that music is from an area settled by many Scots.
Father of Bluegrass music Bill Monroe? (Munro.)

Or maybe not so odd. There is a type of Mountain personality/attitude (some not all) that is shall we say definitely not cosmopolitan.