Often protest groups functioned as useful idiots for other agents, sometimes unbeknownst to them.
Been so long since I’ve read “Radical Son” that I don’t recall any examples from Dave’s experience.
I once attended a Nuclear protest rally on the Central Coast of California.
There were more professional protesters bused in from the Bay Area than there were locals.

One thing is certain:
Every idealistic event included one or more malevolent characters there to work out their personal or other unstated agendas.