Public office hours at startup school are unprofessional?

After today's startup school public office hours, I had the chance to talk to Qasar Younis and expressed to him that I thought the way he conducted public office hours was unprofessional. (to be clear, this specifically involves public office hours in front of thousands of people, not private and group office hours)

What we agree on:

- The partners genuinely want to help startups to succeed

- It's best to be completely honest and never sugar-coat things

- Public office hours was designed to be helpful to both attendees and the startup on stage

- The content of the office hours feedback was productive

What we disagree on:

- Qasar claims that if you can't handle public office hours onstage, you wouldn't cut it with a VC and you probably aren't the founder type. I disagree. Example: Mark Zuckerberg probably would have fumbled over a public office hours appearance early in his facebook days (he's since become a much better communicator).

- Qasar was not open to considering changing the public-only office hours format, even when I asked if I could send him a few ideas in an e-mail. He said YC has been doing this for 10 years and it won't change. Why refuse to even look at possible suggestions?

There are more professional ways to criticize a founder's idea or UI in front of thousands of people other than embarrassing them rapid-fire ambush style, regardless of whether or not the founders know exactly what they're getting into. For example, what about a public office hours that shows and explains the improvement from a previous office hours? This seems much more of a realistic scenario, given that YC office hours are periodic.