Say it. When your child sticks that penny in the socket, like you told him not to - what do you do? Say nothing? NO. You reinforce the lesson by reminding him that you told him not to do that, that this is why, and that he should listen to you better next time. It doesn't have to bemean or ugly at all. It can be said lovingly. But it needs to be said. If they're not listening to you, it's because they are accepting the message of the world. And evil runs the world. I'll happily offend 50 people if it means one hears the truth and is saved from destruction by it. Say it.