Maybe you should hold an intervention. Of course, unfortunately, the brainwashing done in MLM is stronger than any drug addiction, and in many cases more costly.

Wish your friend the best, let him try to build the so called riches from signing up a downline, and wait for him to learn from failure. If he is a good salesperson and actually selling product, maybe he will actually sell enough to save his credit and self respect.

Part of the brainwashing (and you can see it with the MLM answerers in yahoo question alone, some of whom will be likely calling me names) is that anyone who doesn't agree with their view is either "negative", "unintelligent", or just a "non believer destined for failure". You see, they set up their mindset to be completely closed minded from opposing views, so the only way your friend is going to come to his senses is on his own accord. Most people will only take so much failure before they come around, hopefully that is the case with your friend as well.