telling everybody not to use a business and to continue to do so until you get your way IS WRONG.
In fairness the OPs post doesn't actually say that IMO.
It was asking what people thought & if it was a reasonable stance of Sigma to take to not honour a sale once it had made it & taken the money off the purchaser. The thread developed from there, but that was how I was reading the original posting.
To compare Sigma to Wiggle is hardly a fair comparison too
Isn't that the whole point of internet trading - that you are as good as the shop front you put out there & the manner in which you handle your transactions in the public realm?
They didn't handle the transaction very well initially & you would not expect other retailers to act in the same manner surely?
If a retailer is not prepared to treat every purchase like it matters & accord your customers some respect & at minimum some adherence to trading standards (i.e. making a refund when you can't honour a transaction) then you should expect to get feedback based on those actions.