It's a critique of the progressive liberal left from the traditional far left. Central to Fisher's thesis is that by emphasizing race and sex, class identity (which he feels is crucial) is ignored: "I’ve noticed a fascinating magical inversion projection-disavowal mechanism whereby the sheer mention of class is now automatically treated as if that means one is trying to downgrade the importance of race and gender. In fact, the exact opposite is the case, as the Vampires’ Castle uses an ultimately liberal understanding of race and gender to obfuscate class."
What I find particularly interesting is how similar this critique is to the alt-right's criticism of neo-liberalism. I think it's a fine example of the "horseshoe theory" of politics, where the far-left and far-right share certain commonalities: https://en.wikipedia.org/wiki/Horseshoe_theory.