This guy wasn't attacking people, only saying 9/11 was an inside job.
As Joph said, if this is actually the case, then he's got plenty of legal avenues to pursue. I'm just pretty skeptical that this is *all* he was doing.
As for your analysis, you're over thinking things. The police don't all have to be on the conspiracy. How do you know they aren't there to deal with troublemakers like this guy.
Because (and I'm going out on a limb here since I haven't seen the video), the whole point of this is to claim some kind of targeted persecution of this particular guy because of what he was saying. If the police were treating everyone who was simply expressing their free speech the same, then the story isn't really about keeping the truth about 9/11 from being heard, is it?
Again, I'm going out on a limb, but I'm betting that's why you care about this story, right? If this guy had been waving a sign about abortion, or darfour, or freeing Nelson Mandela, or bringing back Menudo, you wouldn't care or even have noticed. It's not a conspiracy theory if it doesn't include persecution of your own specific pet theory about something. Thus, your whole argument rests on the assumption that the police did single him out for what he was saying, and not how he was saying it.
It's not a story otherwise, right? Where's the follow up showing hundreds of other people also arrested for speaking out about their various causes as well?
The content of what was said by this man is irrelevant.
It's not irrelevant to you though, is it?