A business is only as good as it's employees. For your average bike shop (or really anything for that matter) good help is probably hard to find. Especially if your talking low wage hourly employee.
A mistake was obviously made by the employee, but it's hard to tell if it was an innocent mistake that the OP just took the wrong way, or his comments were really offensive. It's not hard to see either scenario playing out. We've all had people rudely insert their opinion in when it wasn't asked for, and we've all had it happen innocently as well.