These people work in this building every day, this is their second home, this situation was abnormal to them, they didn’t respond unreasonably.
edit: I agree with Sundazes, the guy is an ass.
I think they only responded the way they did because of the camera. Had he not been holding a camera or had he been video taping surreptitiously, I expect he would have had far less (maybe no) trouble. I despise double standards - the government was taping all public areas so why is it such a big deal for the public to video tape public areas?