be on (one's) soapbox(redirected from was on his soapbox)
be on (one's) soapbox
To be sharing one's opinions in an impassioned, impromptu manner, often to others' annoyance. (Soapboxes were once commonly used as makeshift platforms for such speeches.) Once grandpa was on his soapbox about the local election, I found an excuse to slip out of the room.
be/get on your ˈsoapbox(informal) express the strong opinions that you have about a particular subject: Don’t mention the Internet in front of him, or he’ll get on his soapbox and we’ll be here all night listening to his opinions about the evils of modern technology.
A soapbox is a small box that somebody speaking in public, especially outdoors, might stand on so that they could be seen and heard more easily.