The interview started with the most mundane question "Who are you?", and the very first sentence of Wales is either a lie or misleading. The journalists asks for clarification (thats a journalists job, btw), and in his second sentence of the interview Wales insults the journalist. I'm pretty sure who is the jerk here.

It also was Wales who bought up the topic, not the journalist. If he considers it a stupid topic he does not want to talk about, why is it the very first thing he talks about?

Sanger was originally hired to edit Nupedia, a web encyclopedia project with a strict peer review process, and only worked for Wales for about a year. Wikipedia was started as a side project (with Sanger contributing to the concept and some early organizing), but Wikipedia quickly became much more successful while Nupedia basically never got off the ground. My impression is that Sanger wanted to impose his own vision on Wikipedia, but couldn't because the community of volunteer editors disagreed, and when Wales stopped paying him as a full time Nupedia editor (Wales's company was tight on cash at that time), he stopped any involvement. This was long before most of the actual work of Wikipedia happened, and that should have been the end of the story.

But ever since, Sanger has been trash talking Wikipedia as a project and community ("broken beyond repair") and trying to undermine it. A few years later he started a competing project (which was predictably a total failure). For two decades he has been promoting himself as "cofounder of Wikipedia". Interviewer after interviewer asks the same lazy questions about the subject, without ever adding any new insight. (You can see that Sanger's ghost is chasing Wikipedia even into this discussion.)

It's beating a dead horse, and entirely off the topic of what the interview was supposed to be about. Answering the question clearly and accurately takes a lot of time and finesse, which is wasted on the interviewer and most of the audience. Wales clearly screwed up in that interview, but it's not hard to see where he's coming from, psychologically.

"So, who are you?" "Stupid question."

What an interview! I had never seen this clip before, it's really something. Facts and context are important for sure, but as someone who isn't clued in on the Sanger drama, Wales could not possibly have made himself look worse. And in under a minute!

As you said, the interviewer is in the right, carrying out the job of interviewing, by pushing Wales as he did. To call him a "jerk" is silly, I think.