You don't see how this paper, which identifies one group in particular as favoring their own interests over democratic governance, is at odds with your thesis that there two symmetrical sides are at fault here?
Or how, from a historical perspective, your labeling our era as a high point of identity politics is grossly ignorant of American history? White supremacism predates the founding of the nation, let alone Tumblr.
From I what I gather from reading the abstract it seems that the paper focuses only on one nutjob side and its authoritarianism. So when someone asks if this the idpol I'm talking about my reply is, sure, yes, one of them.
OK, so who are these two nutjob sides. One is white supremacists. That's easy. You can trace that lineage back to the beginning of American history. The President is on that side, alongside Fox News, Roseanne Barr, etc. That's Jim Crow, the Klan, slavery, the Know-Nothings, Indian Reservations, and on and on.
The other is....social justice warriors? Who is their leader? Hillary Clinton? She was the candidate of the "white working class" in 2008, her turn to the rhetoric of social justice was transparently phony to anyone who had followed her political career. Barack Obama? He spent practically his whole first term trying to find a Republican that would like him and his entire presidency trying to convince your average Fox news voter that he wasn't a member of Nation of Islam. What's their media, MSNBC? That's your typical partisan press. Who is their rank and file? Your average member of the #Resistance cares a million times more about Russia than microaggressions or intersectionality. This tendency exists almost entirely on college campuses, right wing media, and the internet--and I have a strong suspicion that virtually all of your knowledge of American society and culture comes from the internet. What historical current do they represent? "Social justice" would imply they are continuing the legacy of the Civil Rights movement, the suffragettes, the abolitionists, etc, but I doubt you would agree because those are generally agreed to be good things.
When you actually situate these "sides" historically, it's obvious that they aren't equivalent, that one is deeply rooted in the national identity and the other falls apart as a concept the moment you start picking at it.