When someone preaches some truths, you use this phrase (usually in comment sections online) as a way of agreeing.
For instance on Facebook you may have:
Person A: "You should never blame a whole group of people for the actions of a few people within that group!"
Person B: Say It Again Louder For The PeopleIn The Back.
Take care of yourself and take care ofyour family. What do the rest of the people mean to you they don’t mean anything to you. They’re just serfs, they’re just people.