Dear Anonymous Conference Referee,
Thank you very much for pointing out the two grammatical/spelling errors in my most recent conference submission. I wholeheartedly agree that grammatical errors reflect poorly on a paper and demonstrate a degree of sloppiness. I appreciate your attention to detail in this matter.
However, may I suggest that in the future, if you are going to point out someone's grammatical and spelling errors, that you check your own response for grammatical and spelling errors as well. It is generally bad form when your response contains more grammatical/spelling errors than the paper you are critiquing.
Have a nice day!