So what? Graham isn't talking about all that other stuff! He's just talking about "things people make a part of their identity" (for whatever reason, whether that's by choice or through a failure to resist outside pressure), and what the possible negative effects can be.
I frankly don't care that Graham is rich and influential and maybe has an easier time of controlling what he thinks of himself than other people do. "Keep things out of your identity" is useful advice, even if some people will unavoidably find that harder to do because of their social/economic status.
And I disagree that it applies to very few conversations. This can easily apply to the big stuff, like what some people are talking about in other threads on this post, when it comes to dealing with issues that affect marginalized groups. I think people like that are a fine example of when it can be hard to keep things out of your identity. As much as your identity (I prefer "core self-image", which I think is clearer) is your choice, often external factors will pressure you into choosing in certain ways. But I think it does harm discussions about those topics when people have made it such a core part of themselves that they can't see what kinds of persuasion other people would respond best to. I unfortunately see that sort of thing pretty often.
Put another way: yes, Graham is probably the kind of person for whom it is not hard to set his own identity without all that much outside pressure. He's rich and influential. Other people will get put into boxes and groups by others who are more powerful than they are. And these less-powerful people will have a harder time keeping those things from seeping into their own identities. But that doesn't change the (IMO) correctness of Graham's message that it is useful to resist that pressure, even if it's harder for some people to do so.