I emailed him about his book Machinery of Freedom in my 20s (15+ years ago) and he was willing to engage in good faith debate with a complete nobody on the internet who emailed him out of the blue. He was not remotely pretentious or insufferable.

Illusions of grandeur in every paragraph.

For what it's worth, I've met him, and he's very nice in person. He seems to genuinely enjoy talking with strangers about topics of mutual interest.

I've met several academics / ideological celebrities who were indeed insufferable. It's hard to determine this solely from someone's writing.

Probably true to the people who go around asserting false claims and enjoy people pretending to believe them because of their social status. But those people are also insufferable twats to the logical argument types.