My friend, when I bit the bullet and had FB for a couple of years to keep in touch with a loved one who only had phone service when they were by free Wi-Fi, there were Black Bloc groups on there that used FB groups for organizing action. Then Zuc shut them down, and notably not other equally controversial groups. Please.
If you're talking about bad actors wearing ski masks just to sow violence in an otherwise non-violent protest, then yes, maga assholes are a real thing.