Regardless of any impact you may or may not produce we are discussing very different things here.
To say you can harm someone (small or large I really don't care) by soliciting the help of other website owners (whether knowingly or unknowingly) where you are abusing their offered services to create economic sabotage on a 3rd party ... you cannot really "suggest" you cannot be held accountable?
I don't buy that. I sure love to see you win that in a court of law.
A ponzi scheme is a great deal for the early adopters but that doesn't mean it is legal.
Sadly, academic debate will not produce an absolute answer... but I believe the economic cap of Neg SEO is a couple of people will try it... learn that a positive result does not imply a sustainable result and also learn the law can harm them much more easily.
It is easy for you to make a decision to "risk it" for yourself... you are unlikely to sue yourself if you lose... correct?
But when you intentionally "risk it" to do harm to others - I'm sure you can find a way but that is judged on a different scale so it isn't fair to say "if I can to this to myself" - "others can do it to others".
Can you... sure OK I'll agree some morons will try... will you?