I'm not sure why you think this is relevant; it's not. If I have a right to be somewhere and someone asks me and another person to leave, the person leaves and I don't, I still have the right to be there. That someone else listened to the guards is irrelevant.
In your opinion. But your opinion is based on a partial video and a news article. The District Attorney seems to disagree with you. Despite seeing the full video, reading all the eyewitness testimony, and being familiar with the layout of the space and the presence (or lack of) signs, etc. He felt that the guy either did nothing wrong or that despite the video and eyewitnesses he could not prove the guy did anything wrong.
In your opinion. But if he had a right to be there then he had a right to stand up for that right. You don't have to leave when asked if you are somewhere that you have a right to be. Now we know that it is alleged this was a private area (although there seems to be no evidence that it was clear to everyone this area was private), so we know he didn't have the right to be there. But that's not what matters, what matters is whether the proper signs were posted letting it be known that this is private property. If the signs weren't there, you aren't required to listen to a security guard who is claiming the bench you're sitting on is private. We don't know what signage there might have been, but we do know the District Attorney chose to drop the charges, therefore we know he felt his case was not provable.
I agree with you on this. I don't approve of such tactics. But these tactics, pioneered by right wing libertarian groups, are legal. A bad idea? Yes. Harmful to society? Yes. But illegal? No. Worthy of being tased over? No.
He may have been a douchebag for taking this route, but cops don't get to tase people for being douchebags. If they do, they are abusing their power.
Luckily we have someone who weighed in on this case who has seen all the video evidence, all of the eyewitness testimonies, and (most likely) pictures of the area and all the appropriate signs. This person also happens to be a professional who works in the legal field and has a team of people who research the law for him. This person, the District Attorney, reached the conclusion that the evidence that existed (video, eyewitness testimony, photographs, etc.) wasn't enough to prove this guy did anything illegal.