Telling a jerk to f off may satisfy the ego, however, not escalating a verbal confrotation is the best way to avoid getting shot, assulted, run over,etc. by some wacko. Far fetched? ya maybe but you never know. Why take the chance? Smile, be polite, and walk away if the person turns into a jerk. Your loved ones will be happy you made it home in one piece, and you will feel beter too.