How do we know it was private property? From some of the comments made I formed the impression that the event was taking place at a College or University, which would make it public property. If so the reporter was well within his rights and the security guards or police could and should be sued for false imprisonment (aka false arrest).
Placing handcuffs on a person constitutes the act of an arrest. His movements were restricted to the physical placement of the officers who placed the cuffs on him. In fact, false imprisonment is accomplished by simply detaining a person beyond the time necessary to properly identify the person. That is the Law.
He was obviously not causing a disturbance nor was he blocking anybodies passage.
If he was on private property the procedures for invoking trespass was not followed. In order to invoke trespass the person must be informed that they are persona non grata and told to leave the premises. If, after several warnings, the person doesn't remove themselves from the property, they are then trespassing. This man was not told, during the film clip, that he was not welcome on the property and that he must vacate. He was told he was restricted to a specific area. For that restriction to have legal force it must be conspiculously posted for public view. I saw no signs designating such restrictions.
In either case, the actions taken by the uniformed officals was unlawful and unconstitutional.
I've noticed that most liberals react emotionally instead of factually. Emotionally we see one thing, factually it is often something quite the opposite. I would say that that is the defining trait between liberal and conservative: emotion verses reason.