This is what surprises me about the interview. I was under the impression that, given his interest in politics, he was pretty well-informed. But his answers here are consistent with someone who knows very little about the topics he's being asked about, but has a bit of experience arguing with other people ("I'm going to answer your question with another question").

edit: And I'd love to believe the contrarian thing, but when I've seen it done by well-informed people, it's immediately substantive and really thought-provoking, instead of... well, whatever this is.

I'd be very interested in reading the interview you mentioned, if you find it at any point!

Being informed isn't a passive state, but an active one. One of the dangers of getting a reputation for being knowledgeable is that it creates the risk of buying into your own mythology and slacking on the activity on which the reputation was built.

Coupled with the fact that knowledge is often much narrower and more domain-specific than the reputation for knowledge that it produces, and it's quite easy for someone who has, due to time and energy invested in one domain (plus generally-applicable rhetorical skill), built a well-justified reputation for knowledge to end up turning out to be quite ill-informed (if still rhetorically skilled) in other domains in which they have an interest and choose to be an active pontificator.

Expertise is generally pretty narrow. For instance, I heard him speak about bio and pharma about half a year ago and he made several statements that were categorically incorrect and poorly reasoned through.

This sounds like evidence that his knowledge is wide, not narrow

No, making statements outside of his primary domain that are categorically incorrect isn't a sign of broad knowledge. It may be a sign that he thinks his knowledge is broad when it isn't, but there are other explanations.

It's evidence that he's willing to talk about a wide range of topics, not that he has great knowledge in those areas.

That may just means he's a good debater not that he is well informed.