On the first point, Amazon should strictly prohibit gifting free Vine items to others. It is inherently antithetical.

On the second point, no. I don't think it's possible to give free items to people and get honest reviews. The free-ness will often induce either charity or laziness in reviewers. The only way to get an accurate review on a product at its price point is to sell the item at its price point in the wild.

You may want to chalk this up as a lesson about positioning and price anchoring well learned. But with that said, it doesn't change the fact that your response as a brand to what is honestly a very minor setback was alarmingly disproportional and customer hostile. What would you do if you get hypothetically successful and Behringer rips you? What if you tore into the wrong reviewer and they put you on blast to their 80k twitter followers to get you de-platformed? There are a million ways your product can get torn to shreds even if people /like/ it. Is this really the hill you want to die on?