My (male) friend quit Facebook over all the candle parties he was being invited to. For reference, we are mid-thirties in the DC region and most of our peers graduated from a four year college (and many have higher education).
I hide people who spam too much and will unfriend if they automatically add me to their virtual sales parties. I don’t say anything to them directly.
I fundraise for charity once a year and I do post to social media about it several times and email people once (often using the list of previous donors). I realize this is annoying and try to be polite and unobtrusive. I’m thrilled when someone donates even a small amount. The difference with MLM is that it is ongoing and until the seller quits, they are going to be pressured to spam all their friends more and more to meet sales goals and sustain income. I could spend $10 on a candle once to support a friend, but it becomes unsustainable very quickly as more and more acquaintances start selling.