Let's just look at it with common sense... if people were free to "speak" whenever or wherever they want then that's a free pass to ruin any speech or discussion, and that would be just insane bullshit.
Let's say during that sitdown interview with Steve Jobs and Bill Gates a few years ago some Linux asshole just starts spewing bullshit about how Windows and Mac sucks.
Do people really think Linux man is allowed to do this?
What a fucking disservice that would be to both the audience and the speakers... Let him talk outside or hand out fliers, but he can't set up his own fucking podium in the crowd!