This blog has gotten a few hits recently from people looking for leftist critiques of identity politics. I suggest starting here:
"The limits of anti-racism" by Adolph Reed Jr.
"Why Anti-Racism Will Fail" by Rev. Thandeka
"Race, class, and "whiteness theory"" by Sharon Smith
"The Trouble With Diversity" by Walter Benn Michaels
Years ago, I had asked a few of my academic friends for precisely such critiques. Arthur suggested Robert Hughes' Culture of Complaint, which was indeed enjoyable, but other than that, they didn't have any further suggestions, and the political blogosphere, with its tendency to encourage echo chambers and tribal signifiers, was no help. Along the way since then, I've picked up a few useful insights on the topic from conservatives and formulated some rudimentary ones through my own effort, but it's a pleasant surprise to just stumble over something like this, all wrapped up nice and pretty with a bow on top. I read Michaels's book a few months ago (found it so-so), but the rest are new to me.
I had seen perceptive comments from Shetterly on Freddie deBoer's blog, and now, looking over more of his posts, he seems to be interested in many of the same topics, from groupthink to cognitive biases, that I've been fascinated by lately. Check him out, I think you might find it worthwhile. You're already reading here, aren't you? This could only be a step up.