Maybe it's time to fight fire with fire. Every time he mentions this crap, let him know about the great opportunity you have for him in your Amway network. Or Herbalife. Or whatever. Pitch it long and pitch it with gusto, complete with brochures, follow-up emails, invitations to motivational meetings, etc. Let him know that is where you've invested your own money
"Sorry, the stock market is for losers. I'm in control of my own destiny now! I just need 3 more people in my downstream and for each of them to recruit three more people and I'm set. These are the best (soaps, vitamins, cell phone plans, seed packets, whatever) you can buy. Get onboard! I'll call you tomorrow with more info. Hey, what was your brother's email address? Great guy, I met him at your house 5 years ago. "