There is no evidence that they were not customers, he simply claimed he was not able to identify them as customers.
As someone who was once sued in Texas by a scummy publicly traded company for my alleged to be defamatory comments I posted online about their pumped up and soon to collapse revenue, I can assure you that companies can and do lie in their assertions to the court. In my case the intent, plain as simple, was to stifle public discussion of the company so investors could continue to be bamboozled by glowing press releases.
The case was tossed out of court because they had no jurisdiction over me in Texas so we didn't get to the point of having to prove it was a SLAAP suit with no substance. And the company's stock soon collapsed as it became obvious that they were in fact exactly what I and others were asserting that they were.
While I am sympathetic to a company being defamed online, I think we need to give great deference to the right of people to anonymously speak out. There is no even playing field in most cases, companies tend to have more money than the average consumer and if criticism is met with a lawsuit it serves to chill speech to a substantial degree.