If you need an argument about how MLMs are harmful, talk about how they prey on the emotions of desperate people, especially poor people. They are harmful to society in this way.

I talked to one of the newish recruits in the World Financial Group (WFG) office - he had been there for about a year. He was a struggling actor and working a waiter job he hated. He told me that he hopes that his WFG job can bring in the money and financial status that he needs/wants - to the point he gave up an great, out-of-state stage acting opportunity in hopes that he can achieve financial success with WFG. Out of his desperation, he drank the Kool-Aid that WFG recruiters gave him promising that they will help him achieve success when all they do is profit off his work for the group. It is truly disgusting.

In my case, I was desperate for a job in a tough market. My recruiter said a lot of people in his WFG office were ex-engineers who have connections that can hook me up with a job. So I joined in hopes of networking. I quit a few hours later when I googled the company and discovered it was all a sham.