Being in a business means that you have to take both positive and negative feedbacks. If you had handled your customer in a bad way and a customer left a negative feedback about you, the correct attitude is to learn from your mistake and improve. Coming to a customer's blog to flame them for leaving a negative feedback doesn't improve your company image.
Mailboxuk should really learn something about this from other companies.
Check out their childish comments on my negative yet true post about them
I'm not going to entertain these kids because I have much more better stuffs to do in reality =)