The group was a 'mob' in the sense that they were a bunch of 'seminar callers' there to disrupt the tour just as the 'seminar callers' that call radio talk shows aren't doing so to further debate or ask honest questions but to disrupt the show. Reciting questions from a script and not listening to the answers is classless and tacky approach.
If this were a group of union members disrupting a George Bush Q&A, it would most certainly be called a 'mob' by those defending this group of people.
Regardless, it is in very poor taste and shows a lack of class to pepper a tour guide with seminar caller questions that you really have no intent to listen to the answers to. This tour guide was more educated and better prepared to deal with the seminar caller questions, but it's still tacky and classless. It's on the same level of ambush journalism.
If George Bush holds a Q&A open to the public, and he's asked a lot of questions, even by (gasp!) union members!, well, that's pretty much what I would expect. In fact, he's asked hostile questions by reporters shouting at him all at once and it's called a "press conference".