I remember years ago - like 10 years or something crazy - I was in my early twenties, a young woman getting started in the hobby and I sent an item to the wrong person. They started a thread on me in the BOI, threatening me, demanding refunds, etc, etc. There was no email evidence where they had asked for a refund, they had received the animals just fine, and then a few days later there's a picture of an emaciated gecko claiming it was the one I sent them and I was a terrible keeper and owner, and needed to be avoided. It was a horrible experience, and being young and not understanding, I felt like a terrible person. I refunded their money, I was out the Paypal fee, an animal, and my money. It really did a number on my conscience and I stopped trading and selling except in person.
I'm a wee bit older now, and wee bit wiser, and I think you did exactly the right thing but putting this out where it can be seen. People like this should be exposed first thing... THEY need to make it right, and it's on THEM to protect their reputation, not you. Threatening and making excuses just proves the type of person they really are... anyone with stand up character would be falling over themselves to make it right. I, for one, would take out an advance on my credit card if I needed to make a customer happy with a mistake I made.
It's a learning experience all around.