There is a great bit in the "The Art of Happiness, Dalai Lama” book, a western psychiatrist posing questions. At first, unable to understand, how could you show compassion to somehow who is rude or robs you. But if you think through what kind of person would mock someone with a stutter, that person is surely a very bitter and very sad person indeed. Seeing them like this, actual means you are less likely to intellectually accept their comments, as just the rantings of the sick person.