Identity politics comes from a group feeling that their identity is being threatened, is unwanted or is held in contempt. Sometimes that feeling is justified and sometimes it's not. But that's been part of white people in the south for a long, long time.

You're right. It's not new. But something is clearly going on.

I was at the protests a while ago when the confederate flag at the the Columbia, SC, state house grounds was moved to the top of the state house to a monument in front of it. There were essentially two protesting sides: pro-flag, who thought the flag shouldn't be moved; anti-flag, who through it should be removed entirely from the grounds. (I was anti-flag.) The theme of that protest years ago matched closely to what was happening in Charlottesville, except instead of the statue of a confederate general, it was about the confederate flag.

So maybe it's enlightening highlighting the differences to what I hear about what happened in Charlottesville. In the South Carolina protest:
. the pro-flaggers numbered in the dozens, not the hundreds. They were vastly out-numbered by the anti-flaggers.
. the pro-flaggers were clearly not local, as in from the city. They smelled of alcohol, were dirty and unkempt, rude, and basically fit every stereotype of rednecks from the South. (I say that coming from a long line of rednecks myself.)
. there was no violence. There was not even a hint of the possibility of violence.
. the anti-flaggers were roundly mocked. There was a group of men dressed as Southern belles who did a fine job of mocking the other side. Mocking seemed to me to be an effective way to counter the other side.
. no one was yelling at anyone. There were chants and things like that, but no one was getting yelled at directly.

Clearly, something is going wrong when this protest from years ago - about very much the same thing - was so different from what happened in Charlottesville. I'm inclined to agree with OP that the identity politics from the left is feeding into antagonism that is being amplified by reactions on both sides. I don't buy into the notion that the election of Trump has "emboldened" racists that were just lying in wait. Absolutely, there are and continue to be racists, especially in the South, but this is a problem that should be getting better, not worse. So why isn't it?