this is a tricky one...
no, they shouldn't beat on her.
BUT they're in the middle of a violent protest. Her claim of "just asking them to be nice"... well, she's creating a distraction, too. When a few of the guards approach her to talk, that creates an opening elsewhere for bad guys to act up.
And she is protesting. She's not walking to the store or going to work. She's in the middle of a crowd getting rowdy. The whole crowd can say "I was just asking them not to be rough..."
The dude did over-react... he belongs behind a desk or not working at all.