Well that depends highly on what's considered a crime in a protest, who determines that, and whether or not the person in question agrees with the protest.
I have no problem at all catching porch pirates. I have big, big ethical concerns with surveillance footage being used to track public organizers who haven't committed any crimes.
I think these sticky situations are always going to be a problem as long as the Police insist on operating in opposition to the people they claim to want to protect. Police do not feel like they are part of my community, they feel like an upper class of citizen who are permitted to, well, police the community by any means necessary up to and including violence, with basically no oversight.
That's not someone to look to for help. That's someone to fear.