Wow, he does seem like a massive jerk in that video. That said, I try not to judge people on how they acted in the past, but how they currently act. Compare that more recent interview and videos (like Mark Rober's) and he seems to have mellowed out a lot. Maybe it's all for the cameras and he's privately still a massive jerk, I don't know, but my impression of him lately based on stuff I've seen online has generally left a good impression.

He is not speaking personally in that video but after hours of coaching by lawyers. He sounds rude the same way a suspect refuses to speak without a lawyer is rude.

To me it is clear that Gates was prepared by a host of lawyers, which makes sense.

But the interrogator doesn't grasp the subject entirely as well, I too would want clarification to the question if a content provider uses IE. You could ask a helpful question, e.g. Do you mean if they develop sites specifically for IE?

But That is not how you go about a deposition, you're not there to help people build a case against you.