It depends on what the parent was referring to by "identity politics." Some people use that term to mean politics according to demographic factors they cannot

It depends on what the parent was referring to by "identity politics." Some people use that term to mean politics according to demographic factors they cannot directly control, such as their race. So, if it was what was intended, then I don't think your (actually quite excellent) critique of post-modernism is relevant to what they were talking about. Unless of course, you're arguing that it's the underlying philosphy even if the participants in it don't know it or think that way consciously.