Yeah, showing them a melted plug from a power strip at the shop did it for my neighbor. It’s like what @tara642 said, that burnt plastic and wire just clicks in a way words don’t. They finally got why overloading those things is a bad idea.
Showing them the scorch marks on an old, frayed extension cord did the trick for me. That visual of the melted insulation and the darkened copper wire made the danger feel real in a way just talking about it never could. They finally understood why we shouldn't just wrap cracked cords in more electrical tape.