If you go into a church an see a minister speaking from a high platform, he's speaking from the pulpit.
Pulpit was originally used to refer to the platform in a church that a preacher speaks from, but we often use it metaphorically for any kind of preaching, whether it's religious or not. If someone is trying to tell everyone else how to live, they're speaking from the pulpit, whether they're preaching the embrace of root vegetables or warning us that we will be attacked by aliens.
