One of the useful lessons I have learned in life has been to learn to I-G-N-O-R-E (I call it my mantra) people who are rude and sarcastic to me. I can guarantee that once you turn away from them, they are actually left shocked because all they want to do is to provoke and when that provocation does not work, they are left wondering as to what to do next.
They are most likely to feel ashamed by this bad behavior of theirs and might, just might think twice before doing it to another person. Of course nature of human beings don't change so easily but it is definitely worth a try. At least that may be an experience they would remember.