It doesn’t matter what he states. It could still be true that he got 2 returns while his sales dropped by 40%. You logical error still stands on it’s own:
The point you're missing is:
1. Any loss in sales or returns have to be
directly attributable to Amir/Erin's reviews to satisfy the first element of the argument.
2. Even
if they are somehow directly attributable, the review has to contain provable underlying malice or intent to defame to satisfy the second element, because...
3.
Bad reviews of speakers naturally result in lowered sales in a free market, and there's nothing illegal about that. It's only if the company can prove that the review was created with the intent to cause damage to the company that loss of sales or returns due to the review
even come into the equation.
Amir is correct that if Eric states that his customers don't rely on this data or care about his review, he is directly arguing against his own legal theory of lost sales, because he's eliminating the possibility of attribution. Of course, if Eric actually believed that his customer base of "audiophiles" doesn't care about the objective data or reviews, he would have no need to ever engage those producing the reviews... and yet, here we are, watching the self-immolation in realtime.