They’re so sure they’re right they don’t care what anyone says. Questions work. Study what you can find on the Internet and by searching archives here for Quackstar, er, well, you know. Then ask questions that will make him think. If you ask a question he can’t answer, it’ll go to his upline. It’s important to distinguish between their responses and actual answers. For example, if you ask why it’s not a pyramid scheme, they go into a long pitch about why other companies are pyramids, so instead of settling for that, say, “That tells me why other companies aren’t pyramids, but if you keep building more under you, why aren’t YOU a pyramid.” It’ll take a long time to get through to him because he’s so programmed he thinks he has the answer and won’t see what you’re getting at, but if you do this over and over with a lot of the different lines they use, it might make him think enough that he could start doubting.
I’ve “run the numbers” on this stuff in quite a few posts. While IBDrones, er IBOs, won’t listen to the numbers, still, knowing them and using them to make others think with questions can help.