I would imagine that not having any weapon at all (The mentioned knife was in his friends pocket) would be an affirmative defense to a weapons policy citation, but I've been wrong before.
I commend the protester's keeping of the cool. The worst it got on their part was his friends snarky "Would you like a free copy of the US Constitution" (which made me laugh). In the video they come off as calm and reasonable, and the security comes off as aggressive and bullying. So good protest.
I am looking at having to go back and take a couple courses on my local campus to finish my degree, and I see all these videos of campus life these days and wonder if I can get through 4 classes on campus without being expelled. I'm not as tolerant of aggressive, cock-sure stupidity as I was in my 20's.
ETA: ^ That's why it's important to come off as the reasonable one when protesting. This was a win for his group. Had he started cussing, and yelling about "Muh Rights!" on camera, the school very well may have doubled down on their officer.