haranguer

a public speaker who delivers a loud or forceful or angry speech

type of:
orator, public speaker, rhetorician, speechifier, speechmaker
a person who delivers a speech or oration

The insides of Metro stations, which aren’t considered public forums, are off-limits not only to political campaigners, leafleters and soapbox haranguers but also to artistic performers, although station managers sometimes look the other way.