My own personal favourite was one of Nathan's retorts to an unhappy diner; "Oh well, guess we won't be seeing you again then", delivered with trademark teenagerish smirk. I mean, for goodness sake! Would you seriously want to eat in an establishment with staff like that?
All those who decry the lack of emphasis upon the cooking credentials of the winners seem to be excusing the complete lack of FOH credentials in the losing side. Surely both are of equal importance in the contest, which would leave both sides, at best, evenly matched.
In my own personal experience, nothing has put me off any restaurant quicker than poor service or surly staff.