MLM itself is a legitimate business strategy. However the subject of ethics can be rather vulnerable. The pyramid scheme, unlike MLM, is clearly a scam. In a pyramid structure, a member pays a fee to join. A portion of the money will then be remitted back to them when they bring a new member into the scheme. No products are involved in this scheme, simply get more people to dump in money for your chance to make more money.
Many companies provide scripts to help you sell the product or service. While these can be helpful in teaching you about your product and dealing with objections, sales is all about being a solution to what a customer needs. By qualifying your contact first, and then listening to their needs, you can tailor your pitch so that you're the solution to their problem. 
The overwhelming majority of MLM participants (most sources estimated to be over 99.25% of all MLM distributors) participate at either an insignificant or nil net profit.[12] Indeed, the largest proportion of participants must operate at a net loss (after expenses are deducted) so that the few individuals in the uppermost level of the MLM pyramid can derive their significant earnings. Said earnings are then emphasized by the MLM company to all other participants to encourage their continued participation at a continuing financial loss.[13]
Use a tool. You should not be explaining everything about your opportunity or whatever it is you have to sell over the phone, point them to a video, sizzle call, event in their area, anything but you try to explain it all over the phone. You can say “The first step to see if this is even a fit for you is to watch our short overview video at ________________”