You can always respond with a letter like this:
“Please forgive me for not accepting your rejection letter. At this time I cannot accept a rejection of my short story. I accept more than 99 percent of the rejections I receive. Many I don’t agree with, but I realize that accepting a piece of fiction for publication is a very subjective judgment call. My acceptance of your rejection letter is also a subjective process and therefore I am returning your letter to you.
I did read your letter. I read every letter I receive. Your letter was well-written, but due to time constraints from my own writing schedule, I am unable to make editorial comments. I do make mistakes. Don’t you, as an editor, be disheartened by this role reversal. The road of publishing is long and tedious. You need successful publications and I need for successful publications to print my stories. I will expect to see my story in your next publication. Good luck in the future.”
(Hat tip: Helen Rittelmeyer)