the.com/firebrand
A person so passionate they double as their own arson investigation.
means Someone who stirs up trouble or revolution with fierce, agitating zeal.
from Literally a burning stick of wood, once carried to light fires; by the 1300s the flaming metaphor leapt to people who set arguments and movements ablaze.
Old senseMeant an actual torch or smoldering ember.
TheologyA sinner saved became a brand plucked from burning.
PoliticsReserved for agitators too hot to ignore.