Certainly!
The flashbangs would work too, I just wish they were a tad more effective, but I found that if you overwhelm the man with the sign and quickly deal with him somewhat isolated from the crowd using 6-10 officers, it apparently doesn't trigger the aggressiveness in the other AI. Only when it turns into a drawn out struggle does the crowd go nuts.
Which I think it's to the credit of the devs on the vanilla side, the AI behavior is actually pretty interesting.
I guess the main bummer here is after you arrest the man with the sign, the crowd lingers. I'm not sure if it expects you to arrest everyone marked as a demonstrator or not because after arresting the man with the sign, the callout is cleared successful. Some are just bystander AI at that point so as long as you get them off the street, it's all good. I'm certain it might clean itself up if you focus on another area of the map, but this I haven't tried since during the sessions as I only enable the one callout. I have arrested multiple protesters using the surround and overwhelm method and still managed to keep the crowd from going agro.
Super fun to do, I might do another video and let the crowd grow as big as they can get. Though, the danger there is that I recall that years ago I hit a limit where the AI just completely freezes and stops responding, not sure where that limit is or if it's related to computer power since the last time I did this I had a quarter of the power I do now.