The poor guy sealed his own doom. He acted like an ass by waving his hands in the cops face and probably yelling at him. He was obviously a little upset for being woken up and then made maters worse by resisting detainment. If he had been acting calm the cops might not have felt it was necessary to cuff him while they figured out what was going on.
Whoever gave him permission to be there should have informed the security guard, who's job it is to secure the building.
I've witnessed hundreds of people getting cuffed by law enforcement. They do it for a number of reasons, but basically it's to detain the individual until they can figure out what happened. They don't legally need to prove shit at that time. No crime needs to proven before they can cuff you, and no law is violated if they cuff you and it turns out they made a mistake. They just release you with with an apology. Unless you can prove the detainment was done with malice or to harass you then no crime was committed.
There is NEVER an instance in the US when the suspect being place in custody has ANY legal right to negotiate with law enforcement, or have it explained to him why he is being placed in custody. In the US, your legal obligation is to comply, let yourself be cuffed and, if applicable, dispute the action later in court after the immediate situation has been resolved.
I'm not a big fan of what happened on this tape. I'm sure the cops could have handled it a bit more delicately, as I'm sure if the guy had been calmer it might have ended without the fighting.
But the cop haters in this thread are living in their own world if they think US law enforcement doesn't have the legal right to detain people in cuffs while an investigation is conducted.