The warning isn’t valid and if you were in a courtroom you could be sued for making unsubstantiated and slanderous claims regarding someone’s business matters.
This is not a courtroom. And the trust rating is not slander (defamation), which would require the author to be deliberately lying with an intent to harm. That's not what happened here. The feedback is based on publicly available facts.
On the other hand, you keep insisting that you've "done thousands of dollars of business on this site" but you have nothing to show for it. What you have in your post history contradicts that - loan request, fiverr "business", some failed auction, "services" no one seemed to be interested in, $25 gift card, etc - nothing to indicate trustworthiness. And the "service" you got red trust for fits
that pattern, not a pattern of "thousands of dollars of business".