One of the defenses often used by misguided enthusiasts is what I named "Red Herring Definition Defense", or if I'm in a bad mood, the "Wikipedia defense".
Basically, your opponent, instead of trying to take apart your supporting evidence, to prove your statement was wrong, your "opponent" just says "you are wrong" then throw a definition (often copied from Wikipedia or other marketing material) at you, and claim that proves they are right and you are wrong.
For example, if you are discussing Amway's comp plan and relevant case laws (such as Koscot, Omnitrition, and so on), quoting the first paragraph of definition of "network marketing" from Wikipedia is a red herring.
If your opponent use this bad argument, it reveals lack of proper analysis of whatever the defender is objecting to, but a "gut feeling" of "you are wrong and this is why", which often, is a sign of "attribute substitution", where the defender *thought* s/he answered the question, but in reality his/her answer is unrelated to the question (but at the moment, sounds related... somewhat). (see end for link to "attribute substitution" explanation)
Another example: If I am arguing for "Smoking is bad for you", quoting definition of "tobacco" does not hurt my argument (or help your argument) in any way. Thus, it's a red herring.
The arguers sincerely believe what they are arguing for, but sincerity, in this case, is still irrelevant.
Here's yet another example of a a "red herring definition defense".
In response to
an analysis I wrote about AiYellow, and how it may be violating multiple US MLM laws with its current compensation plan, at least two supporters of AiYellow post what they considered to be rebuttals.