First, define immoral in this context. Do we need another government agency to protect us from the bad people? If the government does for the gullible what they have done for the poor, we are doomed. Maybe we should have an agency that allows only businesses with a 50% success rate to get a license. Maybe the poor and gullible can buy into a scheme with a failure rate of 99.99999% that is endorsed by nearly every government on this planet. There must be some anecdote to gullible-ness somewhere!?!? Hmmm....
Second, the vast majority of people that sign up do so to use the products. Probably 80% did not start with any real interest in selling product. There is also a high percentage on top of that who only sign up because of the relationship and have no interest in the product nor having a business. In other words, an extremely high percentage of those numbers you show don't reflect the fact that the vast majority (90% or more?) never had any intention of becoming profitable.
Third, if you know the kind of people that generally are interested in looking for a business that requires little investment and can be done part time, I think it comes as no surprise that it is rare for them to become profitable. There is a small percentage that are profitable up front as they exhaust their own circle of influence, but quickly move on to the next thing when thousands don't show up at their door begging to take their money. A business takes work and dedication and to be blunt, this is not the means to find those kinds of people unless you churn through the mountains of hay to find a couple of needles. This is not immoral or even wrong. McDonalds on the other hand has a strict application process that weeds out 99% up front. The fact is, 95% don't have what it takes to start AND run a successful business. Most of those like to try (and fail) with businesses that cost almost nothing to "give it a try".
Finally, it seems our society is always looking for a victim and someone to blame. I personally don't think an MLM is the way to profitability, but hey, more power to you.
The only proven anecdote for most of the problems we face is found in gaining knowledge of true principles and applying them through hard work and becoming charitable and forgiving.