There's two ways of reading this. You can read it from a technical perspective and take the message of something along the lines of "Don't invest your ego into unnecessary technical questions because it'll stop you having logical and productive discussions". But if this were written today in the context of something like this SE issue you could read it as tone deaf - a trans-man/women doesn't choose to face discrimination, they don't have a choice over their identity, they merely express their identity, so telling them to "Keep your identity" small is basically akin to saying that they shouldn't express their identity - something that PG as a straight white male doesn't have to worry about.
Disclaimer: It was written in 2009, read in context it's very clear the first interpretation is the correct one, there's an entire concept of identity that didn't exist in the public discussion when this was written.
I see what you mean. I guess perhaps another way of characterizing PG's advice would be to keep your identity as small as possible, but no smaller.
I think it's a pretty good idea to think about how to not be a "Java programmer" or a "kitesurfer" (to pick two things that I could be identified as), since the former sets my brain up to be implicitly against, say, Kotlin or Haskell, and the latter sets my brain up to be against windsurfing. And I like all of those things too!
But certainly, there are things that are core to someone's identity, and I guess that's where each of us needs to find our own boundaries.
Not that I expect this to become universal mores, but wisdom traditions from Buddhism to Deleuze advise us (generally speaking, blurring important distinctions) to have no core identity.
Identity can be a tool and a crutch. My feeling (as someone who identifies as human and has been hanging out/coping with the world for 3-4 decades -- a feeling, informed by a lifetime of good and bad situations) is that identity politics hurts more the identity-assertion people; the opposite faction is merely annoyed.
PG's essays contain a good amount of quote-unquote "real talk". His SJW-isms espoused on Twitter and the like are obviously only superficial, a defense mechanism widely recognized as a necessity among semi-known, substantially-wealthy persons.
This is pretty common amongst business leaders; comparing their statements against their serious work quickly shows that it's not all so warm-and-fuzzy.
Virtue signaling may be its own reward to the masses, but it serves a real function for the well-to-do in preventing or at least confusing a Marie Antoinette effect. If there's any "let them eat cake" to be found, they can point to an abundance of more recent "truth to power" statements that will create enough ambiguity to tamp down the fervor of the mob, if and/or when it comes to that.
Disclaimer: It was written in 2009, read in context it's very clear the first interpretation is the correct one, there's an entire concept of identity that didn't exist in the public discussion when this was written.