I wanted to fire every customer who called in because of the abusive way they treated the support people. The support people patiently explained to me that it was part of their job and they didn't take it personally.
I have found people are on a grid with "people helpers" as one axis and "problem solvers" as the other. Close to 100% people helper, you know that you can help this person because you've done it 100x. Close to 100% problem solver, you're going out of your mind because you've done this 100x.
It's not like he was being abusive to an individual support staff member, he cussed about the app in an Amazon review and on their forum because it was genuinely failing for him. Nothing wrong with that, people get worked up when stuff doesn't work sometimes, you need to be able to handle some level of that when doing support for your product.
And worse, they're selling a physical product which they just made effectively useless after that customer invested time in installation and setup. Sad to see the warnings about cloud services being abused in this way seem to be quite true.
Companies aren't about the big idea. They aren't about the product. They're about serving other people. To do that, having a big idea and a product can definitely help. But the very easiest way to fuck up a company is to forget that success comes down to a great number of small interactions.
I have been a founder too, and I am aware that this is a lot more stressful than it seems from the outside, and this one star review might have been the last straw.
However, dealing with angry customers is a part of the job (like everything else, until proper employees are hired). Let's say that this person is not particularly good at said job.