Given my own, and many of my friends, calling ourselves some variation on your friend's self-described political views, I think he's being pre-emptively, jokingly snarky, in order to fend off the kind of judgement implicit behind your, "Make of that what you will," from coming into the conversation. If he calls himself a "pinko" or whatever, he's taken its use as an epithet off the table.

That's no small part of why my friends and I do that, anyway.