Other forms: agitators
In politics, an agitator is someone who deliberately gets other people riled up about an issue, encouraging them to protest.
It's a fairly common political tactic to call activists and reformers agitators, implying that they mainly want to cause trouble. When large groups of citizens protest policies or laws, those in opposition sometimes accuse them of being agitators, rather than people who actually believe in a cause. In the 1960s, George Wallace, the pro-segregation governor of Alabama, famously called civil rights activists "paid outside agitators."