I must defend security guard guy a little here. At the very start of the video, you can see the word “security” on his shirt. He is not a police officer. He does not have police powers or qualified immunity if things go south.
Security guards have been criminally prosecuted for laying their hands on people when they didn’t have good enough reason to do so.
A security guard’s job is to observe and report. Physically intervene only when someone is in serious danger. That wasn’t the case here.
Security guard guy is no hero. It would have been nice if he had yelled at the mob instead of just standing there. But I don’t think he committed a firing offense, assuming that he at least called the incident in.
If he had been a campus police officer, it would be a far different story. It would be dereliction of duty, a firing offense.
He should have told the masked people to let the guy enter.