Regarding the KLS yelling event: I'm surprised that fans didn't get involved. It doesn't take but a few people to restrain an individual or calm a person down until the actual security personnel arrives there, rather than letting the situation go on for too long. But, as someone else mentioned previously, people don't want to get involved for fear of escalation or personal attack. I suppose that comes with the job.
The fans did get "involved" in a rather disgusting fashion. The fan in question has a mental disability, and several audience members took it upon themselves to yell at him to get off the stage, to whistle at him, etc. Frankly, I found that behavior from the crowd far more offensive than anything the fan did. When I saw the video of that portion of the proceedings, it literally made me ill. (Commenting on other reactions that offended me would involve violating the board's guidelines about referring to other sites and forums in a negative light, but suffice it to say that this type of behavior didn't end when the event itself ended.)
As to why he was or wasn't banned, there's probably a very simple explanation. None of the actors who interacted with him in the incidents presented here requested it. The response to this fan's behavior reveals far more about the observers' incivility and intolerance than the fan's.
This raises a larger question. Who's to decide what is or isn't appropriate behavior?