I'm going to respond back with sarcasm in response to a customer's sarcasm
Why would you treat a customer this way?
He's rude to me and he deserves it.
When a customer is rude and is sarcastic to you, it is natural to want to give that behavior back. This can lead to many bad outcomes including loosing your job. It is better to just smile and let it go.
That's too hard.
If you can't fake it you should probably look for a new job where you have to customer interaction. Have you never felt frustrated before with a service you were unhappy with? I think a little compassion goes a long way.