I tend to be a bit outspoken on many more subjects that I should and sometimes hear my friends say, "Oh, he is on his soapbox again." Of course, that just makes me talk faster and louder. Ha.
Younger folks have no idea where that saying comes from. The term originates from the days when speakers would elevate themselves above the crowd by standing on a wooden crate originally used for shipment of soap or other dry goods. A person would stand on the box to make an impromptu speech, often about religion, politics, or any other topic about which they wanted to have their opinion heard.
Many times hucksters would get on their soapbox to sell any number of things from snake oil and wonder potions to books. Central Parks were favorite public areas to get on your soapbox and be heard in the days before television and the internet.
Today's equivalent of a soapbox is a blog, or facebook, or twitter, etc. and soap is no longer shipped in wooden crates. Some of us send out regular 'soapbox' emails to anyone willing to 'listen'. Please don't throw rotten tomatoes.
BTW, the original soapbox derby encouraged the use of soap boxes and orange crates to make the cars. Also, 'snake oil salesman' is a derogatory term for people who sell quack medicine or any product with exaggerated marketing, but questionable quality or benefit. I'll bite my tongue on further commentary about that.