The key thing to keep in mind is the designer may be wrong. I'm sure if you ask the store owner they have a totally different story, and it's likely not "We are SUPER EVIL and just stiff people who do good work". Maybe the contractor (onemine.com, if you're curious) tried to bill the store owner more than agreed upon, the store owner refused, and this is the result. Maybe the contractor left out some significant part of the site and the store owner wont pay until completion. Who knows?
The problem here is OneMine has taken all the power in the pay dispute by holding the client's intellectual property hostage until all demands are met. It's at the very least unprofessional, but it becomes defamation very quickly unless OneMine has an absolutely airtight case. There better be exactly zero unfinished products, missed deadlines, rate changes, etc. And it's safe to say with many contract projects this is not the case.