That genius should have been fired on the spot. There is a certain professionalism that should be expected of Geniuses, and belittling customers is way over the line.
c'mon doc. genius's can have a sense of humor too. I took my magic mouse back and handed it to a genius and said,"it's not magic any more". He took it from me and said,"It don't have any batteries in it." We both had a good laugh and then he handed me a new magic mouse.