I've had a similar experience, although probably less-than yours.
I sit in a room with four or five people. We interact as equals, and I always feel like I'm one of five.
Then, someone makes a comment about the south - or adopt a twangy Southern accent - or make an insulting comment about the south - or stupid people from the south - or something that identifies me as different due to the place of my birth recognized because of my accent...
Suddenly, I'm not one of five. I'm not one of them. I'm set apart in an insulting way.
I'm discriminated against because of my "belonging" in a group. That belonging sets me apart from them. I'm a suspect. I'm less than them.
It's not due to anything I've done or said. Like black skin, the way I form words is some outward sign to them that I'm different. As if they started talking about unwed black mothers or saggy pants, every disparaging remark made about people from the south is a side-swipe at me. Innocence of the things that are said matters not.
The indictment is made - indirectly, but as real as a slap on my face.
I don't react well to it.
I should, but I don't because it pisses me off.
No, I don't listen to Rush Limbaugh. No, I don't think blacks are inferior. No, I'm not a Bible thumper.
But, it doesn't matter.
Guilty as charged. I'm momentarily ostracized, bullied, charged, and judged.
If you don't react, you capitulate or cower. If you do react, you look guilty - forced to retaliate or defend your innocent self.
If you enter the conversation - obviously as the canary in the coal mine - you become an object of derisive pity.
If you figure out an acceptable answer, please tell me about it.
Meanwhile, solidarity with you, darling.