It's basic etiquette to not interrupt someone in that manner if they have the podium. Even if he was right, he should've waited. Real douche move to do that to someone's entire presentation. I'm all for speaking your mind in public, and standing up for an opinion, but timing is everything. Yehuda Katz has poor timing.
If he was at a local user group in the first place, then I'd say his timing was awesome, cause despite his obvious rockstar status in the community, he still spends time helping and creating at the base level, and he should be thanked for that.