on a soapbox
Vocalizing one's opinions, beliefs, or ideologies in an impassioned, impromptu manner, often to others' annoyance. Soapboxes (crates in which soap was shipped) were once commonly used as makeshift platforms for such speeches. Uh oh, Grandpa is on a soapbox about local politics again. It always drives the rest of the family crazy! Whenever Jim gets on a soapbox like this, I just try to tune him out.
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